Effect of tempering on microstructure and machinability of AISI D3 tool steel in end milling with PVD-coated carbide tools

Effect of tempering on microstructure and machinability of AISI D3 tool steel in end milling with PVD-coated carbide tools | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effect of tempering on microstructure and machinability of AISI D3 tool steel in end milling with PVD-coated carbide tools Mohamed Zakaria ZAHAF, Nacer MOKAS, Abdelaziz AMIRAT, Okba ABID CHAREF, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7019508/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 13 Nov, 2025 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted 5 You are reading this latest preprint version Abstract The present work highlighted experimental investigation on the effects of tempering on the micrography and machinability of AISI D3 tool steel, generally used for punches and dies in the stamping process, during end milling and dry milling operations. As expected quenching and tempering resulted in improving the mechanical properties. Hardness value in the as received material jumped from 29.1 HRc to up to 61.2 HRc according to the tempering temperature. Effectively as the latter increases, hardness decreases to 48.3 HRc. Relatively, microstructure analyses revealed that carbide particles merged and aggregated according to tempering temperature. EDS microanalysis confirmed the elemental composition of carbide and matrix zones in the microstructure of AISI D3 tool steel, showing a high degree of consistency in all samples examined compared with the initial and post-treatment states. Machinability was characterized by the tool life of TiAlN PVD-coated tungsten carbide inserts (grade GC1030) when milling on a conventional high-rigidity machine tool. The tests showed that increasing the tempering temperature significantly improves the material's machinability for an even better tool life ranging from 72 to 216 minutes at cutting speed 60 m/min. Tempering Quenching End milling Tool wear Microstructure Hardness Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 1. Introduction Heat treatment is essential to guarantee the best performance of tool steels. Many instances of low performance and unexpected failures in practical applications are often attributed to errors in heat treatment. Additionally, the desired properties of tool steels can only be attained through proper heat treatment [ 1 ]. Application of high carbon, high chromium cold work tool steel (AISI D series) has been restricted to the temperatures below 260°C. In this category, there is D3 steel with carbon of 2% − 2.35% and chromium of 11%- 13%, widely used for fabrication of cutting and forming-dies of metal [ 2 ]. Therefore, there are some remained carbides in D3 steel even below the melting point, which increase wear resistance [ 3 ]. The advances of tool materials and rigid machine tools can be used for hard milling of tool steel employed in the manufacture of dies and molds, i.e., milling steels at their fully hardened state at 60 HRc [ 4 , 5 ]. Zahaf et al [ 6 ] highlighted the influence of tool wear and machining system vibration on machined surface quality during finish milling of hardened AISI D3 tool steel with cemented carbide cutting tools in up and down milling modes. Their results indicated that 49 HRc hardening with a cutting speed of 59 m/min resulted in an acceptable surface quality but left the tool 6.5 times more quickly worn compared to milling in the as-received state (31.6 HRc). But displacement evolution analysis and associated tool wear indicated that, in all hardening conditions, the cutter was good at wear resistance until 36 minutes and after that, tool wear was highly sensitive to the hardening condition. Hoseiny et al. [ 7 ] researched the effect of heat treatment on the microstructure and machinability of prehardened mold steel. End milling test with PVD-coated carbide inserts was conducted. They indicated that spheroidization treatment with quenching and tempering led to the best machinability in the form of reduced cutting forces and better tool life. Sousa et al. [ 8 ] studied the wear behaviour of TiAlSiN and TiAlN PVD coated tools in milling of pre-hardened tool steel. They concluded that TiAlSiN coating presented better results in pre-hardened tool steel milling than TiAlN coated tools with optimal cutting speed for wear behaviour was 80 m/min. Tan et al. [ 9 ] studied the influence of repeated tempering on the microstructure and machinability of AISI 52100 steel based on cutting force, cylindricity, and surface roughness. Their results demonstrated that repeated tempering treatment produced a high toughness and an optimal balance of machinability. The lowest cutting force during machining was achieved at the highest cutting speed and the lowest feed rate. Effects of austenitizing temperature, tempering temperature, and multi-tempering on the content of retained austenite (RA) and hardness were examined by Kenevisi et al. [ 10 ]. The results indicated that the lowest value of 732 Hv hardness was achieved by austenitizing at 1040°C and triple-stage tempering treatment at 550°C. Nevertheless, the highest hardness of 801 Hv was achieved by austenitization at 1055°C and three-step tempering procedures of 525°C. It was also noted that increasing the number of tempering steps decreased the retained austenite content in the microstructure. Nykiel and Hryniewicz [ 11 ] investigated the transformations of carbides during the tempering of D3 tool steel using electron diffraction from extraction carbides replicas. They noted that after 120 minutes of tempering at sequential temperatures, there were large primary carbides and small secondary M 7 C 3 carbides, which had not been dissolved during austenitizing. Mochtar et al. [ 12 ] studied the effect of tempering temperature changes on the microstructure, retained austenite content, and hardness of AISI D2 tool steel. They determined that the microstructure phases obtained in the as-quenched, as-tempered, and subzero tempered sample variables are martensite, bainite, retained austenite, and carbide phase. However, the variables that participated in the tempering process displayed a well-organized and finer martensitic phase, also known as the martensitic tempered phase. Besides, finer and more content of fine carbide was noticed with the increase of tempering temperature. Demir et al. [ 13 ] examined the influence of various microstructures, achieved through heat treatment, on cutting forces and surface roughness when turning AISI H13 hot work tool steel. They concluded that heat treatment condition and cutting speed significantly influenced the surface roughness of the specimens. Cutting forces were not, however, influenced by either steel microstructure or cutting speed, except for the water-quenched specimens. Gong et al. [ 14 ] examined the wear and breakage mechanisms of coated carbide tools when milling H13 and SKD11 hardened steels. From their experimental findings, they established that workpiece hardness played the dominant role in determining tool failure modes. Efremenko et al. [ 15 ] carried out the effect of various heat treatments with a goal to establish an optimal softening heat treatment method for high-Cr cast iron for enhancing machinability during drill tests. Based on their findings, they identified that the heat treatment of cast iron by quenching and tempering showed enhanced machinability as compared to other heat treatment processes. Hiremath et al. [ 16 ] studied comparative dry machinability of ferritic-pearlitic, quench-tempered, and bainitic steels under various cutting conditions with respect to composition and heat treatment variation. They observed that ferritic-pearlitic and quench-tempered steels exhibited decreases in cutting forces by 5–12% and machining temperatures by 12–20% in addition of sulfur, although they possess higher strength owing to increased vanadium content. Additionally, the flank wear land width decreased with higher sulfur content in both ferritic-pearlitic and quench-tempered steels. Bai et al. [ 17 ] enhanced the surface finish of additively manufactured (AMed) high-strength maraging steel (18Ni300), both with and without heat treatment. They investigated the impact of microstructure on machinability, examining factors such as microhardness, cutting force, surface roughness, tool wear, and chip formation. Their experimental results exhibited significant machinability differences among various microstructure samples fabricated via AM. The as-built and ageing-treated samples experienced surface microhardness improvement after milling. Cutting force and tool wear were significantly enhanced by ageing treatment, while the as-built samples and the solution treatment ones experienced less effect. The surface roughness of as-built sample deteriorated significantly, improved from closer to 10 µm to less than 0.4 µm when milled. This study is dedicated to optimizing the cutting conditions of coated tungsten carbide tools (TiAlN PVD with GC1030 Sandvik Coromant insert). Tests were carried out on AISI D3 tool steel during milling after heat treatment. The impact of micrography at different tempering temperatures on the machinability of the treated steel and tool life was the response criterion observed. 2 Experimental procedures 2.1 Material and workpiece High carbon and high chromium carbide content, AISI D3 tool steel, commonly used to produce dies and hard moulds has been selected because of its high wear resistance and good cutting performance of specifically think metal sheets. The chemical composition is given in Table 1 . The workpiece is prepared from a drawn 90x90 mm square cross-section that is cut into 50 mm length. Table 1 Chemical composition in weight % of AISI D3 tool steel Elements C Si Mn P S Cr Ni Mo Composition 2.07 0.24 0.29 0.027 0.006 12.21 0.079 0.018 2.2 Heat treatment Heat treatments have been conducted in a 60-liter capacity Nabertherm LH60/12 furnace with five-sided brick heating insulation for maximum energy efficiency. The furnace is equipped with a digital temperature display up to a maximum of 1200°C. The heat treatment process of the workpiece followed the heat treatment diagram illustrated in Fig. 1 : quenching at 960°C for a holding period of 90 minutes for each of the three samples followed by rapid cooling in an oil bath; tempering was performed at three temperatures, i.e., 250°C, 450°C, and 650°C, with a holding duration of 120 minutes for each of the three samples followed by slow air cooling. All tempering operations were performed for a minimum duration of 2 hours [ 18 ]. 2.3 Hardness Tests Quenching and tempering are the final processing steps for tool steels in order to achieve the desired hardness and other properties tailored to the respective steel grade and application [ 18 ]. Usually hardness measurements are used to check the required properties. So, hardness tests were performed on an Indent Durometer model 8187.5 LKV. 2.4 SEM observation Microstructural examination was conducted on four 14×14×14 mm samples prepared from the parent bar. All the samples were polished and etched with 3% Nital solution. The microstructures were examined on a Quanta 250 Scanning Electron Microscope (SEM) to examine the morphology and structural features of the bulk samples as shown in Fig. 2 . The SEM was operated in high vacuum mode, utilizing an Everhart-Thornley Detector (ETD), and was equipped with an Energy-Dispersive X-ray Spectroscopy (EDS) system for detailed microanalysis. 2.5 Machining process and conditions The machining process followed the steps described in author’s previous work [ 6 ]. Machining was performed on a high-rigidity vertical milling machine, model 6H11, with a power of 4.5 kW and a maximum spindle speed of 1800 rev/min. Figure 3 illustrates the schematic arrangement of the hard milling end process. A 25 mm diameter three-insert tool holder was used to fit 3 TiAlN PVD-coated tungsten carbide inserts, equivalent to the R390-11T308M-PM1030 (Sandvik Coromant) designation of grade GC1030. The cutting insert has a corner radius of 0.8 mm and a lead angle of 90°. The corresponding cutting parameters are shown in Table 2 . Table 2: Illustration of the machining conditions applied during the experimental tests 2.6 Tool wear measurement The flank wear of the inserts on the milling cutter was measured using a workshop optical microscope, model MMN-2, which offers a measurement accuracy of 5 µm. The monitoring of the inserts is achieved without the need to remove them from the cutter body. Measurements of wear were made along cutting edge profile, for all three inserts. Figure 4 provides a view of the tool holder setup for measuring tool wear. The wear resistance of both materials was evaluated based on a permissible wear limit of [V B ] = 0.2 mm. Additionally, an optical microscope equipped with a camera, specifically the Motic 2000 model BA210 digital, was employed to observe the wear morphology of the inserts. 3 Results and Discussion 3.1 Effect of tempering on hardness The hardness results are shown in Table 3 . As expected tempering has great influence of the mechanical properties of the material. Relatively to the as received material, all the values of hardness increased after heat treatment. In fact, after quenching, as the tempering temperatures increases from 250°C to 650°C the value of hardness decreases of 0.79% from 61.2 HRc to 48.3 HR. This is in good agreement with literature for the AISI D3 tool steel. Table 3 The hardness values of AISI D3 tool steel samples subjected to various heat treatment conditions Heat treatment Medium hardness of samples Unit HRc As-received 29.1 Quenched and tempered at 250°C 61.2 Quenched and tempered at 450°C 56.1 Quenched and tempered at 650°C 48.3 3.2 Effect of tempering on microstructure 3.2.1 View of microstructure Observation of the texture of AISI D3 steel before and after quenching, using a scanning electron microscope (SEM), revealed a typical microstructure comprising carbide particles classified according to their size into primary carbides (over 5 µm) and secondary carbides (less than or equal to 5 µm), the interpretation of which has been widely discussed in previous work [ 19 – 21 ]. The delivery condition of AISI D3 steel is generally hot-forged or rolled, followed by de-stressing annealing, which reduces its tensile strength and hardness by 10 to 25%, but increases its elongation in the meantime, making it more machinable. Figure 5 a illustrates its texture. Annealing of tool steel aims to produce a soft, machinable microstructure of spheroidized carbides in a ferrite matrix to reduce hardness and tool wear. The treatment eliminates coarse-grained hot-worked structures and deleterious phases like martensite or pearlite that might be formed on cooling [ 18 ]. Carbides present are primary carbides (coarse, formed on melting) and secondary carbides (fine, precipitated at lower temperature), along with spheroidized cementite in a ferritic matrix. EDS element analysis of carbide-rich (α) and matrix (β) areas was carried out. Quenching and tempering at 650°C, 450°C, and 250°C resulted in microstructures comprising retained austenite and tempered martensite, with martensite having partially decomposed to cementite (Fe 3 C) and ferrite. As-quenched martensite (960°C, 2.07% C) consisted of austenite and cementite, which transformed into martensite upon cooling. The microstructure had spheroidized cementite particles (white) and free carbide zones in the martensitic matrix, influencing mechanical properties. The size, morphology, and distribution of carbides (primary/secondary) were critical to steel performance [ 22 ]. In Fig. 5 b, the microstructure formed by tempering at 650°C consists of very fine particles in the martensitic matrix on a scale of 20 µm. However, an astonishing difference occurs as tempering temperatures rise: higher tempering temperatures lead to lower hardness and precipitate carbides to cluster closer together in the martensitic matrix, observed on a scale of 100 µm. This effect begins to appear in Fig. 5 c and keeps on rising relative to Fig. 5 b. In Fig. 5 d, the microstructure includes tempered martensite. On a scale of 5 µm, oxides, being black, are visible between primary carbides in all treated samples. Oxides result in adhesion between carbides, forming bigger primary carbides in the martensitic matrix, which helps in maintaining the strength of steel. These microstructural changes have a direct impact on the mechanical properties and machinability of AISI D3 tool steel. Measurements of carbide sizes revealed that primary carbides averaged 5,827 µm, while secondary carbides averaged 4,420 µm in samples that were quenched and tempered at 450°C. These measurements were consistent across all samples, as illustrated in Fig. 6 . 3.2.2 EDS analysis Figure 7 presents the EDS microanalysis results for the selected zone α, marked on the microstructure. Chromium (Cr) peaks are evident in all samples, both before and after heat treatment. The weight percentages of carbon (C), oxygen (O), chromium (Cr), and iron (Fe) are provided in Table 4 , their atomic percentages in Table 5 , and the total intensity percentages in Table 6 . In both selected zones α and β, carbon (C) is the predominant element in atomic percentage, accounting for nearly half of the composition compared to the other elements (O, Cr, Fe), following a distribution of approximately 50% {C} and 50% {O, Cr, Fe}. This is consistent with the high carbon content (2.07%) of the studied AISI D3 steel. The presence of carbides in zone α is confirmed in Figs. 7 (a, b, c, d). Table 4 Intelligent quantitative results EDS for weight (in percent %) Element Weight Unit % Zone α β Samples AR QT 650 QT 450 QT 250 AR QT 650 QT 450 QT 250 C 24.76 22.43 26.70 21.28 28.26 18.70 28.58 18.82 O 8.61 12.48 13.23 8.69 13.04 13.80 13.20 7.44 Cr 30.82 30.17 28.37 32.41 3.73 4.95 3.19 4.07 Fe 35.81 34.92 31.70 37.62 54.97 62.55 55.03 69.67 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Table 5 Intelligent quantitative results EDS for atomic (in percent %) Element Atomic Unit % Zone α β Samples AR QT 650 QT 450 QT 250 AR QT 650 QT 450 QT 250 C 53.78 48.46 53.40 49.93 55.70 42.83 55.98 53.44 O 14.04 20.25 19.86 15.15 19.30 23.73 19.41 14.34 Cr 15.46 15.06 13.11 13.44 1.70 2.62 1.44 2.38 Fe 16.72 16.23 13.63 21.48 23.30 30.82 23.17 29.84 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Table 6 Intelligent quantitative results EDS for total intensity (in percent %) Element Total Intensity Unit % Zone α β Samples AR QT 650 QT 450 QT 250 AR QT 650 QT 450 QT 250 C 3.81 3.95 5.10 3.94 4.92 3.04 5.63 2.70 O 3.02 5.36 5.39 4.23 4.81 6.33 5.48 3.75 Cr 53.74 51.97 51.92 52.53 9.49 10.87 8.18 8.38 Fe 39.43 38.72 37.59 39.30 80.78 79.76 80.71 85.17 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 The chromium (Cr) peak represents the highest mean total intensity at 52.54% and a weight percentage of 30.44%. Iron (Fe) is second with a mean total intensity of 38.76% and a weight percentage of 35.01%. Trace amounts of oxygen (O) and carbon (C) are detected with weight percentages of 4.50% and 4.20%, respectively. Although iron's weight percentage is ever so slightly higher than chromium's, the value is very small at 4.57%. But relative strength wise, chromium is 13.78% stronger than iron. Therefore, the selected area α is largely characterized by chromium (Cr). The matrix of the selected region β, marked on the microstructure, was identified through EDS microanalysis, as indicated in Fig. 8 (a, b, c, d). The results indicate that iron (Fe) is the dominant element in this zone. There are other elements such as chromium (Cr), carbon (C), and oxygen (O) present. Chromium (Cr) acts as a secondary component in this case, as the ferritic and martensitic matrix contains chromium atoms in solid solution that were not fully consumed during the precipitation of tempering carbides. The mean total intensity percentages for this zone are as follows: iron (Fe) at 81.61%, chromium (Cr) at 9.23%, oxygen (O) at 5.09%, and carbon (C) at 4.07%, as detailed in Table 6 . This confirms that the selected zone β is primarily characterized by its iron (Fe) content. Figure 9 compares the chromium (Cr) and iron (Fe) content in the selected zone α (carbides zone) across all samples, including the as-received condition and those quenched and tempered at 250°C, 450°C, and 650°C. The analysis reveals significant consistency in elemental composition with no to little significant difference in the as-received and heat-treated conditions. The carbides zone, on average, has 57.5% chromium and 42.5% iron. Figure 10 is a comparison of the chosen zone β (matrix zone) contents of chromium (Cr) and iron (Fe). The analysis indicates that on average, the matrix zone has 10.1% chromium and 89.9% iron. This reflects the excellent compositional differences between the carbides zone and matrix zone in the samples in question. 3.3 Effect of tempering on machinability (tool wear) The flank wear criterion was set at a permissible value of [V B ] = 0.2 mm. The cutting tool was considered worn when flank wear reached this value, as per the TS ISO 8688-1 milling standard (Tool life testing in milling), established by the technical committee. This criterion is commonly applied in shoulder milling operations involving high radial depth (aₚ). Flank wear was identified as the predominant type of wear observed during the tests. Tool life evaluations were conducted on heat-treated blocks using the 0.2 mm flank wear criterion (V B max = 0.2 mm) [ 7 , 23 ]. Figure 11 shows the tool life when it reaches the permissible wear of 0.2 mm, as a function of cutting speed Vc for the case of AISI D3 steel in the delivery condition. Indeed, at cutting speed Vc = 60m/min, tool life reached 1027 min, i.e. three times longer than at cutting speed V C =120 m/min, where it did not exceed 330 min. Machinability tests on AISI D3 steel after tempering at different temperatures (250°C, 450°C and 650°C), as a function of cutting speeds Vc between 60 and 120 m/min, are illustrated in Fig. 12 . The results show that increasing the cutting speed increases tool wear, while increasing the tempering temperature enhances tool life. Figure 13 shows the tool life when wear has reached its permissible limit (0.2 mm), as a function of cutting speeds Vc (60 and 120 m/min) for samples tested in the as-delivered condition and after heat treatment. It is noticeable that increasing the cutting speed has a detrimental effect on tool life, as it accentuates wear on the cutting edges of the tool, while high revenue temperatures play in favor of the latter. This behavior is perfectly in line with the literature, since increasing cutting speed leads to a rise in temperature in the cutting zone, which favors abrasive and melting wear, while high tempering temperatures contribute to softening and reducing the hardness of the steel. When comparing the heat-treated conditions, the machining workpiece after quenching and tempering at 650°C with cutting speed of 60 m/min, the tool demonstrated a very long life of t = 216 minutes. The tool wear behavior was effectively controlled by the hardness of the workpiece, and the rates of wear varied according to the change in hardness. Also, the fine-grained microstructure of the material assisted in providing better wear resistance since it enabled the cutting tool to resist wear and deformation more. The delivery condition should also be considered, as it is not comparable to the heat-treated conditions. Figure 14 presents wear photographs captured under the following milling conditions: (Vc = 60 m/min, fz = 0.05 mm/tooth, a p = 8 mm, a e = 0.3 mm). Figure 14 .a displays the flank wear observed during the milling of the steel in its as-received condition. A whitish adherent chip abrasion layer appears on the whole worn strip. It is a protective film for the tool during machining with adhesion phenomena followed by abrasion, which finally leads to the removal of particles from the substrate. Figure 14 .b indicates the wear observed during milling of the steel in the quenched and tempered condition at 250°C. The insert wear is milder with fewer chips sticking and greater abrasion scratches. This can be explained due to the higher material hardness (61.2 HRc). Compared to the wear in Fig. 14 .b, the wear in Fig. 14 .c, obtained during the milling of the steel quenched and tempered at 450°C, exhibits similar characteristics. Abrasive wear with slight plastic deformation is observed on the cutting edge, together with the initial development of notch wear (depth-of-cut line wear). In Fig. 14 .d, for the steel quenched and tempered at 650°C, the observed wear is less severe compared to the previous cases. However, the formation of notch wear appears to occur prematurely. This is explained by the fact that, in the quenched and tempered state at 650°C, the hardness decreases with depth relative to the surface layer of the material. Figure 15 presents wear photographs captured under the following milling conditions: (Vc = 120 m/min, fz = 0.05 mm/tooth, a p = 8 mm, a e = 0.3 mm). Figure 15 .a displays the flank wear observed during the milling of the steel in its as-received condition. When the cutting speed is boosted to 120 m/min, the chip adhesion layer is removed and the flank wear increases considerably. This is attributed to the decreased material hardness (29.1 HRc) and increased plasticity. The wear belt exhibits extreme abrasion wear. Figure 15 .b illustrates the wear observed during the milling of the steel in the quenched and tempered state at 250°C. The wear on the insert is less severe compared to the as-received condition, but the cutting edge deformation is more noticeable. Significant abrasive and adhesive wear mechanisms are clearly evident. In Fig. 15 .c, the wear observed during the milling of the steel quenched and tempered at 450°C is more uniform, characterized by abrasive wear with adhesion. The cutting edge displays slight plastic deformation together with emerging notch wear. The tool wear characteristics for the 650°C quenched and tempered steel are illustrated in Fig. 15 .d The wear is less severe, but several chip detachments from the substrate are noted. This can be explained by the presence of highly concentrated and extremely hard chromium carbide grains in the AISI D3 steel quenched and tempered at 650°C. Conclusion The investigation focused on tempering influences, with the following key results: Microstructure composition: The quenched and tempered samples exhibited a microstructure dominated by tempered martensite and retained austenite. Temperature dependence: The study revealed that carbide particles merged and aggregated when tempering temperatures rose from 450°C to 650°C. At 650°C, the high-temperature effect caused the formation of very fine particles distributed in the martensitic matrix. Comparison of hardness: The results show tempering's significant influence on the mechanical properties of the material. All the samples showed higher hardness values after heat treatment compared to the as-received material. Tempered martensite was softer compared to quenched martensite. Consistency of the elements: The elemental composition between all the samples was highly consistent according to the EDS analysis, with chromium and iron being principal elements of treated and untreated AISI D3 tool steel. Material machinability: The material was determined to be more difficult to machine at tempering temperatures of 250°C and 450°C. At 650°C, the material was determined to be easier to machine with a hardness of 48.3 HRc. With a cutting speed (Vc) of 60 m/min, fz = 0.05 mm/tooth, a p = 8 mm, and a e = 0.3 mm, a very high milling time of t = 216 minutes was achieved. This means that increased tempering temperatures minimize the machining difficulties regardless of the material’s hardness. These observations demonstrate temperature-dependent microstructural evolution during tempering, revealing determinative effects on carbide redistribution and matrix phase refinement. Microstructure evolved after tempering at 650°C presents very fine particles, which make the carbides closer in the matrix. Moreover, the fine-grained structure enhances wear resistance via the improvement of cutting tool wear resistance. Machinability was thus optimized accordingly. Declarations All authors declare that they have no conflicts of interest. Acknowledgements This study was conducted as part of the project titled "Optimization of the machinability and mechanical properties of heat-treated metals". The authors wish to thank the research laboratory of advanced technology in mechanical production of the badji mokhtar university faculty of engineering sciences and the research laboratory of the higher school of mining and metallurgy in annaba, algeria, for support and facilities. References Mesquita RA, Barbosa CA, Machado AR (2017) Heat Treatment of Tool Steels. 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Wear 266:297–309. https://doi.org/10.1016/j.wear.2008.07.001 Torkamani H, Raygan Sh, Rassizadehghani J (2014) Comparing microstructure and mechanical properties of AISI D2 steel after bright hardening and oil quenching. Materials and Design 54:1049–1055. http://dx.doi.org/10.1016/j.matdes.2013.09.043 Kursuncu B, Caliskan H, Guven SY, Panjan P (2018) Improvement of cutting performance of carbide cutting tools in milling of the Inconel 718 superalloy using multilayer nanocomposite hard coating and cryogenic heat treatment. Int J Adv Manuf Technol 97:467–479. https://doi.org/10.1007/s00170-018-1931-z Cite Share Download PDF Status: Published Journal Publication published 13 Nov, 2025 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted Editorial decision: Major Revisions Needed 18 Sep, 2025 Reviewers agreed at journal 27 Jul, 2025 Reviewers invited by journal 02 Jul, 2025 Editor assigned by journal 01 Jul, 2025 First submitted to journal 01 Jul, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7019508","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":479635580,"identity":"a44b1bfc-5425-4116-969f-b5cd0b7a521d","order_by":0,"name":"Mohamed Zakaria ZAHAF","email":"data:image/png;base64,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","orcid":"https://orcid.org/0009-0001-3954-8669","institution":"University of Badji Mokhtar Annaba: Universite Badji Mokhtar Annaba","correspondingAuthor":true,"prefix":"","firstName":"Mohamed","middleName":"Zakaria","lastName":"ZAHAF","suffix":""},{"id":479635581,"identity":"013d4239-cd48-4e4f-bd81-70c6c6ed6dc2","order_by":1,"name":"Nacer MOKAS","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Nacer","middleName":"","lastName":"MOKAS","suffix":""},{"id":479635582,"identity":"96a5d310-e493-4567-af1a-9585d322d964","order_by":2,"name":"Abdelaziz AMIRAT","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Abdelaziz","middleName":"","lastName":"AMIRAT","suffix":""},{"id":479635583,"identity":"9c28521e-022c-4f8a-8dce-c19ffcb52191","order_by":3,"name":"Okba ABID CHAREF","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Okba","middleName":"ABID","lastName":"CHAREF","suffix":""},{"id":479635584,"identity":"6fdb3233-cb10-4e30-bd9a-c2275ec2e79f","order_by":4,"name":"Abderraouf KHIRECHE","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Abderraouf","middleName":"","lastName":"KHIRECHE","suffix":""},{"id":479635585,"identity":"dd7c581b-cf7b-4ce4-a16d-0d9432d56cbe","order_by":5,"name":"Hamza RAMDANI","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Hamza","middleName":"","lastName":"RAMDANI","suffix":""},{"id":479635586,"identity":"d700ed7c-3171-4e61-9e8b-8c63366f983f","order_by":6,"name":"Noureddine KACIMI","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Noureddine","middleName":"","lastName":"KACIMI","suffix":""},{"id":479635587,"identity":"fe65a264-e8d3-4847-8fc7-024f22346601","order_by":7,"name":"Said BOUDEBANE","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Said","middleName":"","lastName":"BOUDEBANE","suffix":""}],"badges":[],"createdAt":"2025-07-01 10:57:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7019508/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7019508/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00170-025-16933-6","type":"published","date":"2025-11-13T15:57:57+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":86009736,"identity":"1c95e44d-607c-40c3-a067-eb597913986f","added_by":"auto","created_at":"2025-07-04 09:34:02","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":99327,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic heat treatment process applied to AISI D3 tool steel\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/4537ebad62a7a4ae106ab65c.png"},{"id":86009359,"identity":"246338a1-352f-448e-bbc8-749e796bf7c2","added_by":"auto","created_at":"2025-07-04 09:26:01","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":244284,"visible":true,"origin":"","legend":"\u003cp\u003eView of SEM arrangement illustrating the microstructure and EDS analysis of both treated and untreated AISI D3 tool steel\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/5612ba80f4f7a9c5602d1229.png"},{"id":86009384,"identity":"d6d1af7b-d30c-4389-b11b-5d179badc3bd","added_by":"auto","created_at":"2025-07-04 09:26:02","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":206604,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental setup for the hard end milling process\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/2877b42ae5e8008ec5b9e242.png"},{"id":86009360,"identity":"736f8dc2-2529-4aab-867f-0655ce68cfbd","added_by":"auto","created_at":"2025-07-04 09:26:01","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":333316,"visible":true,"origin":"","legend":"\u003cp\u003eEquipment and methods for tool wear measurement and evaluating morphology\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/c191fa8813886f5f8f3ae250.png"},{"id":86009357,"identity":"12b0cff5-4004-4335-ba00-e10cdedf3410","added_by":"auto","created_at":"2025-07-04 09:26:01","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":398275,"visible":true,"origin":"","legend":"\u003cp\u003eSEM observation of as-received and heat treated samples of AISI D3 tool steel\u003c/p\u003e\n\u003cp\u003ea) As-received; b) QT at 650°C; c) QT at 450°C; d) QT at 250°C\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/9ab0a7097d59a9ade114300e.png"},{"id":86009395,"identity":"62d93b7c-0638-41df-abff-9e1f212582b0","added_by":"auto","created_at":"2025-07-04 09:26:03","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":133071,"visible":true,"origin":"","legend":"\u003cp\u003eSEM observation of QT at 450°C with measured the size of carbides in a scale of 10 µm\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/8b2990a3de5a6c5cb0c191d9.png"},{"id":86009363,"identity":"a0296a0a-c253-4e9f-b22f-5ba0e2629669","added_by":"auto","created_at":"2025-07-04 09:26:01","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":208299,"visible":true,"origin":"","legend":"\u003cp\u003eResults EDS Energy-selective X-ray microanalysis system for selected zone α (carbides)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea)\u003c/strong\u003eAs-received; \u003cstrong\u003eb)\u003c/strong\u003e QT at 650°C; \u003cstrong\u003ec)\u003c/strong\u003e QT at 450°C; \u003cstrong\u003ed)\u003c/strong\u003e QT at 250°C\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/459d967731cfe38bed787958.png"},{"id":86009366,"identity":"15c9c9f7-a1a2-4f8b-9f23-5305bfafa40e","added_by":"auto","created_at":"2025-07-04 09:26:01","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":199924,"visible":true,"origin":"","legend":"\u003cp\u003eResults EDS Energy-selective X-ray microanalysis system for selected zone β (matrix)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea)\u003c/strong\u003eAs-received; \u003cstrong\u003eb)\u003c/strong\u003e QT at 650°C; \u003cstrong\u003ec)\u003c/strong\u003e QT at 450°C; \u003cstrong\u003ed)\u003c/strong\u003e QT at 250°C\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/7cc5336009aadaeb8e7e67ba.png"},{"id":86009737,"identity":"86c5a879-a754-4c49-9da5-06590121eac5","added_by":"auto","created_at":"2025-07-04 09:34:02","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":24418,"visible":true,"origin":"","legend":"\u003cp\u003eIntelligent quantitative EDS results for total intensity of the main elements (Cr and Fe) in selected zone α\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/33ecbf47fcffc7ec54ef023e.png"},{"id":86009397,"identity":"d37a147e-20bc-47e2-8e6e-9c7f7baac1dc","added_by":"auto","created_at":"2025-07-04 09:26:03","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":24410,"visible":true,"origin":"","legend":"\u003cp\u003eIntelligent quantitative EDS results for total intensity of the main elements (Cr and Fe) in selected zone β\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/baf6f40b1f66a7e20f63c8da.png"},{"id":86009393,"identity":"e9f4b0dc-fb20-4234-8c6c-f2aa82fe78fe","added_by":"auto","created_at":"2025-07-04 09:26:02","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":23717,"visible":true,"origin":"","legend":"\u003cp\u003eEvolution of the flank wear V\u003csub\u003eB \u003c/sub\u003e(of As-received samples) with milling time at cutting speed of 60 m/min and 120 m/min\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/0a785236d0768dddc8f8a732.png"},{"id":86009367,"identity":"ad65c558-572e-4105-8d31-7133dd88d2df","added_by":"auto","created_at":"2025-07-04 09:26:01","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":33700,"visible":true,"origin":"","legend":"\u003cp\u003eEvolution of the flank wear V\u003csub\u003eB\u003c/sub\u003e (of treated samples) with milling time at cutting speed of 60 m/min and 120 m/min\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/82ba324acb0fb49aa1024174.png"},{"id":86009361,"identity":"7d40307c-5656-455d-a8e4-281fde102ba0","added_by":"auto","created_at":"2025-07-04 09:26:01","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":19786,"visible":true,"origin":"","legend":"\u003cp\u003eComparative diagram of tool life as a function of cutting speed (Vc) for AISI D3 steel in delivery condition and at different tempering temperatures.\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/1f4d0040cc5967bd880eda09.png"},{"id":86009376,"identity":"c6cb5f5f-71cf-40af-9119-f2b33862ac70","added_by":"auto","created_at":"2025-07-04 09:26:02","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":529380,"visible":true,"origin":"","legend":"\u003cp\u003ePhotography and Morphology of flank wear in GC1030 insert for as-received and hardened condition, Vc = 60 m/min, a) As-received; b) QT at 250°C; c) QT at 450°C; d) QT at 650°C\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/3e3f3b26670377c2ada34ae4.png"},{"id":86009742,"identity":"af7d3a5d-df69-4943-b91a-3eab80216e08","added_by":"auto","created_at":"2025-07-04 09:34:03","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":538747,"visible":true,"origin":"","legend":"\u003cp\u003ePhotography and Morphology of flank wear in GC1030 insert for as-received and hardened condition, Vc= 120 m/min, a) As-received; b) QT at 250°C; c) QT at 450°C; d) QT at 650°C\u003c/p\u003e","description":"","filename":"15.png","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/38895da0af7d25ebe866f009.png"},{"id":96105849,"identity":"4c6a0bf4-8d69-461c-b765-85f95230107d","added_by":"auto","created_at":"2025-11-17 16:12:02","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4425504,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7019508/v1/3db1dc1c-9779-4dbb-9463-cf4d3d3ce89b.pdf"}],"financialInterests":"","formattedTitle":"Effect of tempering on microstructure and machinability of AISI D3 tool steel in end milling with PVD-coated carbide tools","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eHeat treatment is essential to guarantee the best performance of tool steels. Many instances of low performance and unexpected failures in practical applications are often attributed to errors in heat treatment. Additionally, the desired properties of tool steels can only be attained through proper heat treatment [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Application of high carbon, high chromium cold work tool steel (AISI D series) has been restricted to the temperatures below 260\u0026deg;C. In this category, there is D3 steel with carbon of 2% \u0026minus;\u0026thinsp;2.35% and chromium of 11%- 13%, widely used for fabrication of cutting and forming-dies of metal [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Therefore, there are some remained carbides in D3 steel even below the melting point, which increase wear resistance [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The advances of tool materials and rigid machine tools can be used for hard milling of tool steel employed in the manufacture of dies and molds, i.e., milling steels at their fully hardened state at 60 HRc [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eZahaf et al [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] highlighted the influence of tool wear and machining system vibration on machined surface quality during finish milling of hardened AISI D3 tool steel with cemented carbide cutting tools in up and down milling modes. Their results indicated that 49 HRc hardening with a cutting speed of 59 m/min resulted in an acceptable surface quality but left the tool 6.5 times more quickly worn compared to milling in the as-received state (31.6 HRc). But displacement evolution analysis and associated tool wear indicated that, in all hardening conditions, the cutter was good at wear resistance until 36 minutes and after that, tool wear was highly sensitive to the hardening condition. Hoseiny et al. [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] researched the effect of heat treatment on the microstructure and machinability of prehardened mold steel. End milling test with PVD-coated carbide inserts was conducted. They indicated that spheroidization treatment with quenching and tempering led to the best machinability in the form of reduced cutting forces and better tool life. Sousa et al. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] studied the wear behaviour of TiAlSiN and TiAlN PVD coated tools in milling of pre-hardened tool steel. They concluded that TiAlSiN coating presented better results in pre-hardened tool steel milling than TiAlN coated tools with optimal cutting speed for wear behaviour was 80 m/min. Tan et al. [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] studied the influence of repeated tempering on the microstructure and machinability of AISI 52100 steel based on cutting force, cylindricity, and surface roughness. Their results demonstrated that repeated tempering treatment produced a high toughness and an optimal balance of machinability. The lowest cutting force during machining was achieved at the highest cutting speed and the lowest feed rate. Effects of austenitizing temperature, tempering temperature, and multi-tempering on the content of retained austenite (RA) and hardness were examined by Kenevisi et al. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The results indicated that the lowest value of 732 Hv hardness was achieved by austenitizing at 1040\u0026deg;C and triple-stage tempering treatment at 550\u0026deg;C. Nevertheless, the highest hardness of 801 Hv was achieved by austenitization at 1055\u0026deg;C and three-step tempering procedures of 525\u0026deg;C. It was also noted that increasing the number of tempering steps decreased the retained austenite content in the microstructure. Nykiel and Hryniewicz [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] investigated the transformations of carbides during the tempering of D3 tool steel using electron diffraction from extraction carbides replicas. They noted that after 120 minutes of tempering at sequential temperatures, there were large primary carbides and small secondary M\u003csub\u003e7\u003c/sub\u003eC\u003csub\u003e3\u003c/sub\u003e carbides, which had not been dissolved during austenitizing. Mochtar et al. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] studied the effect of tempering temperature changes on the microstructure, retained austenite content, and hardness of AISI D2 tool steel. They determined that the microstructure phases obtained in the as-quenched, as-tempered, and subzero tempered sample variables are martensite, bainite, retained austenite, and carbide phase. However, the variables that participated in the tempering process displayed a well-organized and finer martensitic phase, also known as the martensitic tempered phase. Besides, finer and more content of fine carbide was noticed with the increase of tempering temperature. Demir et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] examined the influence of various microstructures, achieved through heat treatment, on cutting forces and surface roughness when turning AISI H13 hot work tool steel. They concluded that heat treatment condition and cutting speed significantly influenced the surface roughness of the specimens. Cutting forces were not, however, influenced by either steel microstructure or cutting speed, except for the water-quenched specimens. Gong et al. [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] examined the wear and breakage mechanisms of coated carbide tools when milling H13 and SKD11 hardened steels. From their experimental findings, they established that workpiece hardness played the dominant role in determining tool failure modes. Efremenko et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] carried out the effect of various heat treatments with a goal to establish an optimal softening heat treatment method for high-Cr cast iron for enhancing machinability during drill tests. Based on their findings, they identified that the heat treatment of cast iron by quenching and tempering showed enhanced machinability as compared to other heat treatment processes. Hiremath et al. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] studied comparative dry machinability of ferritic-pearlitic, quench-tempered, and bainitic steels under various cutting conditions with respect to composition and heat treatment variation. They observed that ferritic-pearlitic and quench-tempered steels exhibited decreases in cutting forces by 5\u0026ndash;12% and machining temperatures by 12\u0026ndash;20% in addition of sulfur, although they possess higher strength owing to increased vanadium content. Additionally, the flank wear land width decreased with higher sulfur content in both ferritic-pearlitic and quench-tempered steels. Bai et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] enhanced the surface finish of additively manufactured (AMed) high-strength maraging steel (18Ni300), both with and without heat treatment. They investigated the impact of microstructure on machinability, examining factors such as microhardness, cutting force, surface roughness, tool wear, and chip formation. Their experimental results exhibited significant machinability differences among various microstructure samples fabricated via AM. The as-built and ageing-treated samples experienced surface microhardness improvement after milling. Cutting force and tool wear were significantly enhanced by ageing treatment, while the as-built samples and the solution treatment ones experienced less effect. The surface roughness of as-built sample deteriorated significantly, improved from closer to 10 \u0026micro;m to less than 0.4 \u0026micro;m when milled.\u003c/p\u003e \u003cp\u003eThis study is dedicated to optimizing the cutting conditions of coated tungsten carbide tools (TiAlN PVD with GC1030 Sandvik Coromant insert). Tests were carried out on AISI D3 tool steel during milling after heat treatment. The impact of micrography at different tempering temperatures on the machinability of the treated steel and tool life was the response criterion observed.\u003c/p\u003e"},{"header":"2 Experimental procedures","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Material and workpiece\u003c/h2\u003e \u003cp\u003eHigh carbon and high chromium carbide content, AISI D3 tool steel, commonly used to produce dies and hard moulds has been selected because of its high wear resistance and good cutting performance of specifically think metal sheets. The chemical composition is given in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The workpiece is prepared from a drawn 90x90 mm square cross-section that is cut into 50 mm length.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChemical composition in weight % of AISI D3 tool steel\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElements\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eCr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eMo\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eComposition\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.027\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e12.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.079\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.018\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Heat treatment\u003c/h2\u003e \u003cp\u003eHeat treatments have been conducted in a 60-liter capacity Nabertherm LH60/12 furnace with five-sided brick heating insulation for maximum energy efficiency. The furnace is equipped with a digital temperature display up to a maximum of 1200\u0026deg;C. The heat treatment process of the workpiece followed the heat treatment diagram illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e: quenching at 960\u0026deg;C for a holding period of 90 minutes for each of the three samples followed by rapid cooling in an oil bath; tempering was performed at three temperatures, i.e., 250\u0026deg;C, 450\u0026deg;C, and 650\u0026deg;C, with a holding duration of 120 minutes for each of the three samples followed by slow air cooling. All tempering operations were performed for a minimum duration of 2 hours [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Hardness Tests\u003c/h2\u003e \u003cp\u003eQuenching and tempering are the final processing steps for tool steels in order to achieve the desired hardness and other properties tailored to the respective steel grade and application [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Usually hardness measurements are used to check the required properties. So, hardness tests were performed on an Indent Durometer model 8187.5 LKV.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 SEM observation\u003c/h2\u003e \u003cp\u003eMicrostructural examination was conducted on four 14\u0026times;14\u0026times;14 mm samples prepared from the parent bar. All the samples were polished and etched with 3% Nital solution. The microstructures were examined on a Quanta 250 Scanning Electron Microscope (SEM) to examine the morphology and structural features of the bulk samples as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The SEM was operated in high vacuum mode, utilizing an Everhart-Thornley Detector (ETD), and was equipped with an Energy-Dispersive X-ray Spectroscopy (EDS) system for detailed microanalysis.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Machining process and conditions\u003c/h2\u003e \u003cp\u003eThe machining process followed the steps described in author\u0026rsquo;s previous work [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Machining was performed on a high-rigidity vertical milling machine, model 6H11, with a power of 4.5 kW and a maximum spindle speed of 1800 rev/min. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e illustrates the schematic arrangement of the hard milling end process. A 25 mm diameter three-insert tool holder was used to fit 3 TiAlN PVD-coated tungsten carbide inserts, equivalent to the R390-11T308M-PM1030 (Sandvik Coromant) designation of grade GC1030. The cutting insert has a corner radius of 0.8 mm and a lead angle of 90\u0026deg;. The corresponding cutting parameters are shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \n\u003cp\u003e\u003cstrong\u003eTable 2:\u0026nbsp;\u003c/strong\u003eIllustration of the machining conditions applied during the experimental tests\u003c/p\u003e\n\u003cp\u003e\u003cimg 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\" width=\"614\" height=\"159\"\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Tool wear measurement\u003c/h2\u003e \u003cp\u003eThe flank wear of the inserts on the milling cutter was measured using a workshop optical microscope, model MMN-2, which offers a measurement accuracy of 5 \u0026micro;m. The monitoring of the inserts is achieved without the need to remove them from the cutter body. Measurements of wear were made along cutting edge profile, for all three inserts. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e provides a view of the tool holder setup for measuring tool wear. The wear resistance of both materials was evaluated based on a permissible wear limit of [V\u003csub\u003eB\u003c/sub\u003e]\u0026thinsp;=\u0026thinsp;0.2 mm. Additionally, an optical microscope equipped with a camera, specifically the Motic 2000 model BA210 digital, was employed to observe the wear morphology of the inserts.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results and Discussion","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Effect of tempering on hardness\u003c/h2\u003e \u003cp\u003eThe hardness results are shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. As expected tempering has great influence of the mechanical properties of the material. Relatively to the as received material, all the values of hardness increased after heat treatment. In fact, after quenching, as the tempering temperatures increases from 250\u0026deg;C to 650\u0026deg;C the value of hardness decreases of 0.79% from 61.2 HRc to 48.3 HR. This is in good agreement with literature for the AISI D3 tool steel.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe hardness values of AISI D3 tool steel samples subjected to various heat treatment conditions\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeat treatment\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eMedium hardness of samples\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHRc\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"1\" nameend=\"c3\" namest=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAs-received\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e29.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQuenched and tempered at 250\u0026deg;C\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e61.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQuenched and tempered at 450\u0026deg;C\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e56.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQuenched and tempered at 650\u0026deg;C\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e48.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Effect of tempering on microstructure\u003c/h2\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e3.2.1 View of microstructure\u003c/h2\u003e \u003cp\u003eObservation of the texture of AISI D3 steel before and after quenching, using a scanning electron microscope (SEM), revealed a typical microstructure comprising carbide particles classified according to their size into primary carbides (over 5 \u0026micro;m) and secondary carbides (less than or equal to 5 \u0026micro;m), the interpretation of which has been widely discussed in previous work [\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe delivery condition of AISI D3 steel is generally hot-forged or rolled, followed by de-stressing annealing, which reduces its tensile strength and hardness by 10 to 25%, but increases its elongation in the meantime, making it more machinable. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea illustrates its texture. Annealing of tool steel aims to produce a soft, machinable microstructure of spheroidized carbides in a ferrite matrix to reduce hardness and tool wear. The treatment eliminates coarse-grained hot-worked structures and deleterious phases like martensite or pearlite that might be formed on cooling [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Carbides present are primary carbides (coarse, formed on melting) and secondary carbides (fine, precipitated at lower temperature), along with spheroidized cementite in a ferritic matrix. EDS element analysis of carbide-rich (α) and matrix (β) areas was carried out. Quenching and tempering at 650\u0026deg;C, 450\u0026deg;C, and 250\u0026deg;C resulted in microstructures comprising retained austenite and tempered martensite, with martensite having partially decomposed to cementite (Fe\u003csub\u003e3\u003c/sub\u003eC) and ferrite. As-quenched martensite (960\u0026deg;C, 2.07% C) consisted of austenite and cementite, which transformed into martensite upon cooling. The microstructure had spheroidized cementite particles (white) and free carbide zones in the martensitic matrix, influencing mechanical properties. The size, morphology, and distribution of carbides (primary/secondary) were critical to steel performance [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. In Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, the microstructure formed by tempering at 650\u0026deg;C consists of very fine particles in the martensitic matrix on a scale of 20 \u0026micro;m. However, an astonishing difference occurs as tempering temperatures rise: higher tempering temperatures lead to lower hardness and precipitate carbides to cluster closer together in the martensitic matrix, observed on a scale of 100 \u0026micro;m. This effect begins to appear in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec and keeps on rising relative to Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb. In Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed, the microstructure includes tempered martensite. On a scale of 5 \u0026micro;m, oxides, being black, are visible between primary carbides in all treated samples. Oxides result in adhesion between carbides, forming bigger primary carbides in the martensitic matrix, which helps in maintaining the strength of steel. These microstructural changes have a direct impact on the mechanical properties and machinability of AISI D3 tool steel. Measurements of carbide sizes revealed that primary carbides averaged 5,827 \u0026micro;m, while secondary carbides averaged 4,420 \u0026micro;m in samples that were quenched and tempered at 450\u0026deg;C. These measurements were consistent across all samples, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003e3.2.2 EDS analysis\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e presents the EDS microanalysis results for the selected zone α, marked on the microstructure. Chromium (Cr) peaks are evident in all samples, both before and after heat treatment. The weight percentages of carbon (C), oxygen (O), chromium (Cr), and iron (Fe) are provided in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, their atomic percentages in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, and the total intensity percentages in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. In both selected zones α and β, carbon (C) is the predominant element in atomic percentage, accounting for nearly half of the composition compared to the other elements (O, Cr, Fe), following a distribution of approximately 50% {C} and 50% {O, Cr, Fe}. This is consistent with the high carbon content (2.07%) of the studied AISI D3 steel. The presence of carbides in zone α is confirmed in Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(a, b, c, d).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eIntelligent quantitative results EDS for weight (in percent %)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"8\" nameend=\"c9\" namest=\"c2\"\u003e \u003cp\u003eWeight\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"8\" nameend=\"c9\" namest=\"c2\"\u003e \u003cp\u003e%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eZone\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e \u003cp\u003eα\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c9\" namest=\"c6\"\u003e \u003cp\u003eβ\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSamples\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eAR\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eQT 650\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eQT 450\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eQT 250\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eAR\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003eQT 650\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003eQT 450\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003eQT 250\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eC\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e21.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e28.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e18.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e28.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e18.82\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eO\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e13.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e13.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e13.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e13.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e7.44\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e28.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e32.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e4.07\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFe\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e35.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e34.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e31.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e37.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e54.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e62.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e55.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e69.67\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eIntelligent quantitative results EDS for atomic (in percent %)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"8\" nameend=\"c9\" namest=\"c2\"\u003e \u003cp\u003eAtomic\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"8\" nameend=\"c9\" namest=\"c2\"\u003e \u003cp\u003e%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eZone\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e \u003cp\u003eα\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c9\" namest=\"c6\"\u003e \u003cp\u003eβ\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSamples\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eAR\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eQT 650\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eQT 450\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eQT 250\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eAR\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003eQT 650\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003eQT 450\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003eQT 250\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eC\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e53.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e48.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e53.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e49.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e55.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e42.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e55.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e53.44\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eO\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e19.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e15.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e19.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e23.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e19.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e14.34\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e13.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e13.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.38\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFe\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e13.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e21.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e23.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e30.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e23.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e29.84\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eIntelligent quantitative results EDS for total intensity (in percent %)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"8\" nameend=\"c9\" namest=\"c2\"\u003e \u003cp\u003eTotal Intensity\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"8\" nameend=\"c9\" namest=\"c2\"\u003e \u003cp\u003e%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eZone\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e \u003cp\u003eα\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c9\" namest=\"c6\"\u003e \u003cp\u003eβ\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSamples\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eAR\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eQT 650\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eQT 450\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eQT 250\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eAR\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003eQT 650\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003eQT 450\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003eQT 250\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eC\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.70\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eO\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e6.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e3.75\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e53.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e51.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e51.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e52.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e10.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e8.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e8.38\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFe\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e39.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e38.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e37.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e39.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e80.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e79.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e80.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e85.17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e100.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe chromium (Cr) peak represents the highest mean total intensity at 52.54% and a weight percentage of 30.44%. Iron (Fe) is second with a mean total intensity of 38.76% and a weight percentage of 35.01%. Trace amounts of oxygen (O) and carbon (C) are detected with weight percentages of 4.50% and 4.20%, respectively. Although iron's weight percentage is ever so slightly higher than chromium's, the value is very small at 4.57%. But relative strength wise, chromium is 13.78% stronger than iron. Therefore, the selected area α is largely characterized by chromium (Cr).\u003c/p\u003e \u003cp\u003eThe matrix of the selected region β, marked on the microstructure, was identified through EDS microanalysis, as indicated in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(a, b, c, d). The results indicate that iron (Fe) is the dominant element in this zone. There are other elements such as chromium (Cr), carbon (C), and oxygen (O) present. Chromium (Cr) acts as a secondary component in this case, as the ferritic and martensitic matrix contains chromium atoms in solid solution that were not fully consumed during the precipitation of tempering carbides. The mean total intensity percentages for this zone are as follows: iron (Fe) at 81.61%, chromium (Cr) at 9.23%, oxygen (O) at 5.09%, and carbon (C) at 4.07%, as detailed in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. This confirms that the selected zone β is primarily characterized by its iron (Fe) content.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e compares the chromium (Cr) and iron (Fe) content in the selected zone α (carbides zone) across all samples, including the as-received condition and those quenched and tempered at 250\u0026deg;C, 450\u0026deg;C, and 650\u0026deg;C. The analysis reveals significant consistency in elemental composition with no to little significant difference in the as-received and heat-treated conditions. The carbides zone, on average, has 57.5% chromium and 42.5% iron. Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e is a comparison of the chosen zone β (matrix zone) contents of chromium (Cr) and iron (Fe). The analysis indicates that on average, the matrix zone has 10.1% chromium and 89.9% iron. This reflects the excellent compositional differences between the carbides zone and matrix zone in the samples in question.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Effect of tempering on machinability (tool wear)\u003c/h2\u003e \u003cp\u003eThe flank wear criterion was set at a permissible value of [V\u003csub\u003eB\u003c/sub\u003e]\u0026thinsp;=\u0026thinsp;0.2 mm. The cutting tool was considered worn when flank wear reached this value, as per the TS ISO 8688-1 milling standard (Tool life testing in milling), established by the technical committee. This criterion is commonly applied in shoulder milling operations involving high radial depth (aₚ). Flank wear was identified as the predominant type of wear observed during the tests. Tool life evaluations were conducted on heat-treated blocks using the 0.2 mm flank wear criterion (V\u003csub\u003eB\u003c/sub\u003e max\u0026thinsp;=\u0026thinsp;0.2 mm) [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e shows the tool life when it reaches the permissible wear of 0.2 mm, as a function of cutting speed Vc for the case of AISI D3 steel in the delivery condition. Indeed, at cutting speed Vc\u0026thinsp;=\u0026thinsp;60m/min, tool life reached 1027 min, i.e. three times longer than at cutting speed V\u003csub\u003eC\u003c/sub\u003e=120 m/min, where it did not exceed 330 min.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eMachinability tests on AISI D3 steel after tempering at different temperatures (250\u0026deg;C, 450\u0026deg;C and 650\u0026deg;C), as a function of cutting speeds Vc between 60 and 120 m/min, are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e. The results show that increasing the cutting speed increases tool wear, while increasing the tempering temperature enhances tool life.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003e shows the tool life when wear has reached its permissible limit (0.2 mm), as a function of cutting speeds Vc (60 and 120 m/min) for samples tested in the as-delivered condition and after heat treatment. It is noticeable that increasing the cutting speed has a detrimental effect on tool life, as it accentuates wear on the cutting edges of the tool, while high revenue temperatures play in favor of the latter. This behavior is perfectly in line with the literature, since increasing cutting speed leads to a rise in temperature in the cutting zone, which favors abrasive and melting wear, while high tempering temperatures contribute to softening and reducing the hardness of the steel. When comparing the heat-treated conditions, the machining workpiece after quenching and tempering at 650\u0026deg;C with cutting speed of 60 m/min, the tool demonstrated a very long life of t\u0026thinsp;=\u0026thinsp;216 minutes. The tool wear behavior was effectively controlled by the hardness of the workpiece, and the rates of wear varied according to the change in hardness. Also, the fine-grained microstructure of the material assisted in providing better wear resistance since it enabled the cutting tool to resist wear and deformation more. The delivery condition should also be considered, as it is not comparable to the heat-treated conditions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e presents wear photographs captured under the following milling conditions: (Vc\u0026thinsp;=\u0026thinsp;60 m/min, fz\u0026thinsp;=\u0026thinsp;0.05 mm/tooth, a\u003csub\u003ep\u003c/sub\u003e = 8 mm, a\u003csub\u003ee\u003c/sub\u003e = 0.3 mm). Figure\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e.a displays the flank wear observed during the milling of the steel in its as-received condition. A whitish adherent chip abrasion layer appears on the whole worn strip. It is a protective film for the tool during machining with adhesion phenomena followed by abrasion, which finally leads to the removal of particles from the substrate. Figure\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e.b indicates the wear observed during milling of the steel in the quenched and tempered condition at 250\u0026deg;C. The insert wear is milder with fewer chips sticking and greater abrasion scratches. This can be explained due to the higher material hardness (61.2 HRc). Compared to the wear in Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e.b, the wear in Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e.c, obtained during the milling of the steel quenched and tempered at 450\u0026deg;C, exhibits similar characteristics. Abrasive wear with slight plastic deformation is observed on the cutting edge, together with the initial development of notch wear (depth-of-cut line wear). In Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e.d, for the steel quenched and tempered at 650\u0026deg;C, the observed wear is less severe compared to the previous cases. However, the formation of notch wear appears to occur prematurely. This is explained by the fact that, in the quenched and tempered state at 650\u0026deg;C, the hardness decreases with depth relative to the surface layer of the material.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e15\u003c/span\u003e presents wear photographs captured under the following milling conditions: (Vc\u0026thinsp;=\u0026thinsp;120 m/min, fz\u0026thinsp;=\u0026thinsp;0.05 mm/tooth, a\u003csub\u003ep\u003c/sub\u003e = 8 mm, a\u003csub\u003ee\u003c/sub\u003e = 0.3 mm). Figure\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e15\u003c/span\u003e.a displays the flank wear observed during the milling of the steel in its as-received condition. When the cutting speed is boosted to 120 m/min, the chip adhesion layer is removed and the flank wear increases considerably. This is attributed to the decreased material hardness (29.1 HRc) and increased plasticity. The wear belt exhibits extreme abrasion wear. Figure\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e15\u003c/span\u003e.b illustrates the wear observed during the milling of the steel in the quenched and tempered state at 250\u0026deg;C. The wear on the insert is less severe compared to the as-received condition, but the cutting edge deformation is more noticeable. Significant abrasive and adhesive wear mechanisms are clearly evident. In Fig.\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e15\u003c/span\u003e.c, the wear observed during the milling of the steel quenched and tempered at 450\u0026deg;C is more uniform, characterized by abrasive wear with adhesion. The cutting edge displays slight plastic deformation together with emerging notch wear. The tool wear characteristics for the 650\u0026deg;C quenched and tempered steel are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e15\u003c/span\u003e.d The wear is less severe, but several chip detachments from the substrate are noted. This can be explained by the presence of highly concentrated and extremely hard chromium carbide grains in the AISI D3 steel quenched and tempered at 650\u0026deg;C.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe investigation focused on tempering influences, with the following key results:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eMicrostructure composition: The quenched and tempered samples exhibited a microstructure dominated by tempered martensite and retained austenite.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eTemperature dependence: The study revealed that carbide particles merged and aggregated when tempering temperatures rose from 450\u0026deg;C to 650\u0026deg;C. At 650\u0026deg;C, the high-temperature effect caused the formation of very fine particles distributed in the martensitic matrix.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eComparison of hardness: The results show tempering's significant influence on the mechanical properties of the material. All the samples showed higher hardness values after heat treatment compared to the as-received material. Tempered martensite was softer compared to quenched martensite.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eConsistency of the elements: The elemental composition between all the samples was highly consistent according to the EDS analysis, with chromium and iron being principal elements of treated and untreated AISI D3 tool steel.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eMaterial machinability: The material was determined to be more difficult to machine at tempering temperatures of 250\u0026deg;C and 450\u0026deg;C. At 650\u0026deg;C, the material was determined to be easier to machine with a hardness of 48.3 HRc. With a cutting speed (Vc) of 60 m/min, fz\u0026thinsp;=\u0026thinsp;0.05 mm/tooth, a\u003csub\u003ep\u003c/sub\u003e = 8 mm, and a\u003csub\u003ee\u003c/sub\u003e = 0.3 mm, a very high milling time of t\u0026thinsp;=\u0026thinsp;216 minutes was achieved. This means that increased tempering temperatures minimize the machining difficulties regardless of the material\u0026rsquo;s hardness.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eThese observations demonstrate temperature-dependent microstructural evolution during tempering, revealing determinative effects on carbide redistribution and matrix phase refinement. Microstructure evolved after tempering at 650\u0026deg;C presents very fine particles, which make the carbides closer in the matrix. Moreover, the fine-grained structure enhances wear resistance via the improvement of cutting tool wear resistance. Machinability was thus optimized accordingly.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAll authors declare that they have no conflicts of interest.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThis study was conducted as part of the project titled \"Optimization of the machinability and mechanical properties of heat-treated metals\". The authors wish to thank the research laboratory of advanced technology in mechanical production of the badji mokhtar university faculty of engineering sciences and the research laboratory of the higher school of mining and metallurgy in annaba, algeria, for support and facilities.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMesquita RA, Barbosa CA, Machado AR (2017) Heat Treatment of Tool Steels. 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Int J Adv Manuf Technol 97:467\u0026ndash;479. https://doi.org/10.1007/s00170-018-1931-z\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"the-international-journal-of-advanced-manufacturing-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jamt","sideBox":"Learn more about [The International Journal of Advanced Manufacturing Technology](https://www.springer.com/journal/170)","snPcode":"170","submissionUrl":"https://submission.nature.com/new-submission/170/3","title":"The International Journal of Advanced Manufacturing Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Tempering, Quenching, End milling, Tool wear, Microstructure, Hardness","lastPublishedDoi":"10.21203/rs.3.rs-7019508/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7019508/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe present work highlighted experimental investigation on the effects of tempering on the micrography and machinability of AISI D3 tool steel, generally used for punches and dies in the stamping process, during end milling and dry milling operations. As expected quenching and tempering resulted in improving the mechanical properties. Hardness value in the as received material jumped from 29.1 HRc to up to 61.2 HRc according to the tempering temperature. Effectively as the latter increases, hardness decreases to 48.3 HRc. Relatively, microstructure analyses revealed that carbide particles merged and aggregated according to tempering temperature. EDS microanalysis confirmed the elemental composition of carbide and matrix zones in the microstructure of AISI D3 tool steel, showing a high degree of consistency in all samples examined compared with the initial and post-treatment states. Machinability was characterized by the tool life of TiAlN PVD-coated tungsten carbide inserts (grade GC1030) when milling on a conventional high-rigidity machine tool. The tests showed that increasing the tempering temperature significantly improves the material's machinability for an even better tool life ranging from 72 to 216 minutes at cutting speed 60 m/min.\u003c/p\u003e","manuscriptTitle":"Effect of tempering on microstructure and machinability of AISI D3 tool steel in end milling with PVD-coated carbide tools","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-04 09:25:56","doi":"10.21203/rs.3.rs-7019508/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revisions Needed","date":"2025-09-18T12:34:21+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-07-27T17:28:22+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-02T12:53:51+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-02T00:25:46+00:00","index":"","fulltext":""},{"type":"submitted","content":"The International Journal of Advanced Manufacturing Technology","date":"2025-07-01T06:57:01+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"the-international-journal-of-advanced-manufacturing-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jamt","sideBox":"Learn more about [The International Journal of Advanced Manufacturing Technology](https://www.springer.com/journal/170)","snPcode":"170","submissionUrl":"https://submission.nature.com/new-submission/170/3","title":"The International Journal of Advanced Manufacturing Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"49bf17d5-42cf-4906-a68f-1f900e92839b","owner":[],"postedDate":"July 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-11-17T16:09:59+00:00","versionOfRecord":{"articleIdentity":"rs-7019508","link":"https://doi.org/10.1007/s00170-025-16933-6","journal":{"identity":"the-international-journal-of-advanced-manufacturing-technology","isVorOnly":false,"title":"The International Journal of Advanced Manufacturing Technology"},"publishedOn":"2025-11-13 15:57:57","publishedOnDateReadable":"November 13th, 2025"},"versionCreatedAt":"2025-07-04 09:25:56","video":"","vorDoi":"10.1007/s00170-025-16933-6","vorDoiUrl":"https://doi.org/10.1007/s00170-025-16933-6","workflowStages":[]},"version":"v1","identity":"rs-7019508","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7019508","identity":"rs-7019508","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}