Microstructural and Chemical Characterization of Industrial Ferronickel Produced by the RKEF Process Using SEM–EDS Analysis

Microstructural and Chemical Characterization of Industrial Ferronickel Produced by the RKEF Process Using SEM–EDS Analysis | 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 Microstructural and Chemical Characterization of Industrial Ferronickel Produced by the RKEF Process Using SEM–EDS Analysis Zarife Bajraktari Gashi, Janna Mateeva This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9561872/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Ferronickel (Fe–Ni) is a key ferroalloy used in stainless steel production, predominantly produced from lateritic ores via the rotary kiln–electric furnace (RKEF) process. In this study, the microstructural features and localized chemical composition of industrial ferronickel produced in Kosovo were investigated using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS).The results reveal a heterogeneous metallic matrix with dendritic morphology, typical of rapid solidification under industrial conditions. SEM observations indicate the presence of non-metallic inclusions embedded within the Fe–Ni matrix. EDS analysis confirms that iron is the dominant element, while nickel is relatively homogeneously distributed, suggesting effective alloying during smelting. Localized oxygen- rich regions are associated with oxide inclusions, likely originating from incomplete slag–metal separation and residual oxides from the reduction process. The presence of carbon is attributed to carbothermic reduction in the rotary kiln stage. The results indicate that reduction reactions are advanced but not fully completed, which is consistent with industrial RKEF operation. By combining microstructural observations with industrial slag composition and process parameters, this study provides insight into the relationship between process conditions, inclusion formation, and alloy heterogeneity. The findings contribute to improved understanding of metallurgical efficiency and ferronickel quality in large-scale industrial production. Ferronickel Lateritic ores Microstructure Pyrometallurgy SEM-EDS Stainless Steel Figures Figure 2 Figure 3 1. INTRODUCTION Ferronickel (Fe–Ni) is one of the most important ferroalloys in modern extractive metallurgy, serving as the primary source of nickel for the production of stainless and special steels. Industrial processing of lateritic nickel ores is predominantly carried out via the rotary kiln–electric furnace (RKEF) route, where the rotary kiln enables partial reduction of oxide phases, followed by high-temperature smelting in the electric furnace to produce molten ferronickel [ 1 , 2 ]. In industrial practice, lateritic ores frequently contain significant inherent moisture and are not always subjected to a dedicated drying stage prior to rotary kiln processing. As a result, additional thermal energy is required for moisture evaporation, leading to increased consumption of carbon-based fuels and reductants. This increased energy demand affects not only the overall energy balance of the process but also the reduction kinetics and thermal stability during the pre-reduction stage [ 3 ]. Recent studies have demonstrated the complexity of carbothermic reduction mechanisms in lateritic nickel ores, including selective reduction of nickel oxides, nucleation of metallic phases, and slag–metal interactions under industrial conditions [ 4 – 6 ]. These processes strongly influence nickel enrichment efficiency and the final quality of ferronickel, which are highly dependent on temperature regime, reductant distribution, and reaction kinetics during both rotary kiln and electric furnace operation. The metallurgical performance of ferronickel is closely related to its chemical composition and microstructural homogeneity. Residual oxide phases and entrapped slag inclusions can adversely affect downstream refining processes and the quality of stainless steel products [ 7 ]. Furthermore, microstructural evolution during solidification governs the distribution of nickel within the iron-rich matrix, influencing alloy uniformity and performance [ 8 ]. Advanced characterization techniques, particularly scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS), are widely used to investigate microstructural features and local elemental distribution in ferroalloys [ 9 , 10 ]. These techniques allow identification of metallic matrices, oxide inclusions, and phase heterogeneities formed during large-scale smelting processes. Despite extensive global research, detailed microstructural investigations of industrial ferronickel produced under full-scale RKEF conditions in Southeast Europe remain limited. In particular, previous studies of the ferronickel plant in Drenas have mainly focused on process evaluation and material balance rather than detailed microstructural characterization [ 7 ]. The objective of this study is to provide a systematic microstructural and semi-quantitative chemical characterization of industrial ferronickel produced under real operating conditions, with emphasis on the relationship between process parameters, slag composition, and alloy quality. 2. MATERIALS AND METHODS 2.1. Industrial process and sampling The investigated material consisted of industrial ferronickel (Fe–Ni) samples collected from a full-scale rotary kiln–electric furnace (RKEF) production line processing lateritic nickel ores in Kosovo [ 7 ]. The analyzed material represents the final metallic product obtained after electric furnace smelting and subsequent refining in the converter. Samples were collected in granulated form under standard industrial operating conditions. Microstructural and chemical characterization was performed using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), widely applied for microstructural investigation and localized elemental analysis in ferroalloys [ 9 , 10 ]. Granulated ferronickel samples were examined in the as-received condition without chemical etching in order to preserve the original solidification morphology. Prior to analysis, selected particles were mounted and prepared for observation. SEM examinations were carried out under high-vacuum conditions using an accelerating voltage of 15–20 kV. Both secondary electron (SE) and backscattered electron (BSE) imaging modes were employed to distinguish between metallic and oxide phases. 2.2. Slag sampling and chemical analysis To evaluate slag composition and metal losses during ferronickel production, industrial slag samples were also analyzed. A total of 31 slag samples obtained from electric furnace operation were considered. The amount of slag produced during individual operational periods ranged between approximately 788 t and 1502 t [ 7 ].The chemical composition of slag samples was determined using X-ray fluorescence (XRF) analysis in an industrial laboratory. The analyzed oxides included SiO₂, MgO, FeO, Al₂O₃, CaO and Cr₂O₃, together with nickel and total iron content. The slag composition is typical of lateritic nickel ore smelting systems and is characterized by a silicate-based matrix. Based on the collected operational data, the average slag composition is presented in Table 1 . Table 1 Average chemical composition of industrial slag (wt.%) Component Content (wt.%) SiO₂ 58.9 FeO 15.2 MgO 17.4 Al₂O₃ 2.4 CaO 2.38 Cr₂O₃ 1.49 Ni 0.083 Fe (total) 11.76 2.3. Microstructural characterization Microstructural characterization of ferronickel samples was performed using SEM in order to evaluate phase morphology, dendritic structures and the presence of non-metallic inclusions. The observations focused on identifying the metallic Fe–Ni matrix, solidification features, and possible oxide inclusions formed during smelting and cooling. The use of EDS imaging enabled compositional contrast between metallic and oxide phases, facilitating phase identification. Microstructural characterization of ferronickel samples was performed using SEM in order to evaluate phase morphology, dendritic structures and the presence of non-metallic inclusions. A representative SEM micrograph of the investigated ferronickel is shown in Fig. 1 . Figure 2 . SEM micrograph of ferronickel (Fe–Ni) with selected point EDS analysis indicating local elemental composition within the metallic matrix and inclusion regions. 2.4. Elemental analysis (EDS) The local chemical composition of ferronickel samples was determined using EDS analysis attached to the scanning electron microscope. Measurements were performed at multiple selected micro-areas (≥ 10 points) within the metallic matrix to improve statistical representativeness.The analyzed elements included Fe, Ni, O and C. Representative EDS results indicate a metallic region composed mainly of iron (approximately 68.6 wt.%), with nickel present at about 5.5 wt.%. Oxygen (≈ 21 wt.%) and carbon (≈ 4–5 wt.%) were also detected in localized regions, indicating the presence of oxide inclusions and residual carbon (Table 2 .). Table 2 Semi-quantitative EDS analysis of a representative micro-area in industrial ferronickel (Fe–Ni) Map Sum Spectrum Element Line Type Weight % Weight % Sigma Atomic % C K series 4.71 0.41 12.92 O K series 21.16 0.30 43.54 Fe K series 68.62 0.49 40.45 Ni K series 5.51 0.35 3.09 The EDS results presented in Table 1 correspond to a localized micro-area within the ferronickel matrix and should therefore be considered semi-quantitative. The analysis indicates that iron is the dominant element, while nickel is present as the principal alloying component. The relatively high oxygen content suggests the presence of oxide inclusions or residual slag phases entrapped within the metallic matrix. Similarly, the detected carbon is attributed to carbothermic reduction processes and possible surface contamination during sample preparation. It should be noted that EDS analysis is sensitive to the analysed micro-volume and may not represent the bulk chemical composition of the ferroalloys (Fe-Ni). Table 3 Industrial production parameters of ferronickel obtained from electric furnace and converter operation Parameter Period 1 Period 2 Period 3 Nickel production (t) 21.59 624.72 5043.90 Nickel production (t/day) 21.59 20.15 13.78 Ni content in ferronickel (%) 17.69 18.07 18.51 Nickel recovery (%) 100.09 98.17 86.49 Energy consumption (MWh) 1204.63 35997.46 318188.84 Specific energy consumption (MWh/t Ni) 55.81 57.62 63.08 *Values above 100% may reflect uncertainties in industrial mass balance calculations and sampling variability The industrial data presented in Table 2 indicate a progressive increase in specific energy consumption from 55.81 to 63.08 MWh/t Ni across the analyzed periods. This trend is accompanied by a decrease in nickel recovery from 98.17% to 86.49%, suggesting reduced process efficiency under later operating conditions. The increase in energy consumption may be associated with variations in ore quality, particularly moisture content and nickel grade, as well as changes in slag composition and furnace operating conditions. Higher FeO content in slag can indicate incomplete reduction, which is consistent with the oxygen-rich regions observed in the SEM–EDS analysis. The nickel content in ferronickel remains relatively stable (17.7–18.5 wt.%), indicating that alloy grade control is maintained despite fluctuations in process efficiency. However, the observed decline in recovery and increase in energy demand suggest that optimization of reduction conditions and slag chemistry could significantly improve overall metallurgical performance. The SEM micrograph (Fig. 1 ) reveals a dendritic metallic structure typical of rapidly solidified ferronickel produced by the RKEF process. The heterogeneous morphology reflects non-equilibrium solidification conditions during tapping and granulation. EDS point analysis (Fig. 2 ) confirms that the metallic matrix is primarily composed of iron with nickel distributed as the principal alloying element. However, the presence of oxygen detected in the analyzed micro-areas suggests the existence of oxide inclusions. Elemental mapping (Fig. 3 ) provides further insight into phase distribution. Iron and nickel are relatively uniformly distributed within the metallic matrix, indicating effective alloy formation. In contrast, oxygen is localized in discrete regions, confirming the presence of oxide inclusions. Carbon appears in localized zones, which may be associated with residual carbon from carbothermic reduction or surface contamination. The presence of oxygen-rich inclusions is consistent with the industrial slag composition and the observed decrease in nickel recovery (Table 3 ), suggesting incomplete slag–metal separation and partial reduction of iron oxides during smelting. 3. DISCUSSION The SEM micrograph (Fig. 1 ) reveals a dendritic metallic structure typical of rapidly solidified ferronickel produced by the RKEF process. The heterogeneous morphology reflects non-equilibrium solidification conditions during tapping and granulation. EDS point analysis (Fig. 2 ) confirms that the metallic matrix is primarily composed of iron with nickel distributed as the principal alloying element. However, the presence of oxygen detected in the analyzed micro-areas suggests the existence of oxide inclusions. Elemental mapping (Fig. 3 ) provides further insight into phase distribution. Iron and nickel are relatively uniformly distributed within the metallic matrix, indicating effective alloy formation. In contrast, oxygen is localized in discrete regions, confirming the presence of oxide inclusions. Carbon appears in localized zones, which may be associated with residual carbon from carbothermic reduction or surface contamination. The presence of oxygen-rich inclusions is consistent with the industrial slag composition and the observed decrease in nickel recovery (Table 2 ), suggesting incomplete slag–metal separation and partial reduction of iron oxides during smelting. 4. CONCLUSIONS Based on the obtained results, the following conclusions can be drawn: Industrial ferronickel produced via the RKEF process exhibits a heterogeneous dendritic microstructure typical of rapid solidification. SEM–EDS analysis confirms that iron is the dominant element, with nickel relatively uniformly distributed within the metallic matrix. Oxygen-rich inclusions indicate incomplete slag–metal separation and partial reduction, consistent with industrial slag composition.The increase in specific energy consumption and decrease in nickel recovery suggest reduced process efficiency under certain operating conditions. The study demonstrates that microstructural characteristics are directly influenced by process parameters, highlighting the importance of optimizing reduction conditions and slag chemistry. Declarations Funding No funding was received for this study. Author Contribution Z.B.-G. conceptualized the study and supervised the research. J.M. (corresponding author) designed the methodology, conducted the experimental work, performed the SEM–EDS analysis, and prepared the figures. Z.B.-G. analyzed and interpreted the data. M.K.A. wrote the main manuscript text. All authors reviewed, revised, and approved the final version of the manuscript. References 5. REFERENCE F.K. Crundwell, M.S. Moats, V. Ramachandran, T.G. Robinson, W.G. Davenport, Extractive Metallurgy of Nickel, Cobalt and Platinum Group Metals (Elsevier, Oxford, 2011) C.K. Gupta, T.K. Mukherjee, Extractive Metallurgy of Nickel, Cobalt and Platinum Group Metals (CRC, Boca Raton, 2007) M.A. Rhamdhani, E. Jak, P.C. Hayes, Phase equilibria and slag–metal reactions in nickel laterite smelting. Miner. Eng. 22 , 311–318 (2009) B. Tang, B. Li, H. Yang, Phase transformation in the metallic reduction process of laterite nickel ores. Metall. Res. Technol. 120 , 291 (2023) Z. Wang, L. Chen, Y. Zhang, Extraction of ferronickel concentrate by reduction roasting–magnetic separation. Mater. Trans. 63 , 1124–1132 (2022) J. Zhang, Z. Wang, Y. Liu, High-grade ferronickel concentrates from laterite ore. Materials. 16 , 7132 (2023) Z. Bajraktari Gashi, B. Halilaj, Material balance of ferronickel production in Drenas. J. Technol. Exploit. Mech. Eng. 4 , 29–35 (2018) C. Rong, J. Zhang, Y. Li, Microstructural evolution of Fe–Ni alloys during solidification. Mater. Charact. 128 , 34–42 (2017) J. Goldstein et al., Scanning Electron Microscopy and X-ray Microanalysis (Springer, New York, 2018) A. Özgür, S. Özdemir, Microstructural characterization of ferronickel alloys using SEM–EDS. J. Mater. Process. Technol. 299 , 117285 (2021) Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-9561872","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":639235355,"identity":"1bcbd714-bad8-41d6-aedb-836180cf53c8","order_by":0,"name":"Zarife Bajraktari Gashi","email":"","orcid":"","institution":"University of Chemical Technology and Metallurgy","correspondingAuthor":false,"prefix":"","firstName":"Zarife","middleName":"Bajraktari","lastName":"Gashi","suffix":""},{"id":639235356,"identity":"aa13aff9-ed50-4e3a-87a3-37e7af232af5","order_by":1,"name":"Janna Mateeva","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyElEQVRIiWNgGAWjYBACxgYYix3GOkCMFrAingNQBiEtCHMlEojUwtzAnfj5Q4VNYv/MN4afP+YwyPHdSCDkMN7NEgfOpCXOuJ1jLHFwG4OxJBFaNkgcbDtszHA7x4wBqCVxAzG2/Dj477+x/M0zYC31xGjZJnGw4YCcwQ0esJYEA4Jamnm3WZw5lixneCatWOLsNgnDmWce4Ndi2N67+UZFjR2P3PHDGz9UbrOR5ztOwBbDZlS+BH7lICBPWMkoGAWjYBSMeAAAbT9LJ1oie0kAAAAASUVORK5CYII=","orcid":"","institution":"University of Chemical Technology and Metallurgy","correspondingAuthor":true,"prefix":"","firstName":"Janna","middleName":"","lastName":"Mateeva","suffix":""}],"badges":[],"createdAt":"2026-04-29 07:23:45","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9561872/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9561872/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":109249596,"identity":"44951167-830b-4ddc-bf61-2d408f71acaf","added_by":"auto","created_at":"2026-05-14 08:57:15","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":91089,"visible":true,"origin":"","legend":"\u003cp\u003eSEM micrograph with selected analysis point indicating the location of EDS measurement within the ferronickel matrix.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9561872/v1/a419d41a8bdbfc15909fa4d0.jpg"},{"id":109242928,"identity":"b0f9d1ca-c61b-4c16-8df5-ab110657908d","added_by":"auto","created_at":"2026-05-14 07:19:59","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":206032,"visible":true,"origin":"","legend":"\u003cp\u003eEDS elemental mapping of ferronickel (Fe–Ni): (a) Fe distribution, (b) O distribution, (c) C distribution, and (d) Ni distribution.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9561872/v1/06e88795ab597c4e58e05fc9.jpg"},{"id":109249609,"identity":"aec838f8-00be-44b9-b865-ac785770443c","added_by":"auto","created_at":"2026-05-14 08:57:29","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":467759,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9561872/v1/bda9afbc-4b2c-437c-aad3-c5c6c03a8d4c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Microstructural and Chemical Characterization of Industrial Ferronickel Produced by the RKEF Process Using SEM–EDS Analysis","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003eFerronickel (Fe\u0026ndash;Ni) is one of the most important ferroalloys in modern extractive metallurgy, serving as the primary source of nickel for the production of stainless and special steels. Industrial processing of lateritic nickel ores is predominantly carried out via the rotary kiln\u0026ndash;electric furnace (RKEF) route, where the rotary kiln enables partial reduction of oxide phases, followed by high-temperature smelting in the electric furnace to produce molten ferronickel [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. In industrial practice, lateritic ores frequently contain significant inherent moisture and are not always subjected to a dedicated drying stage prior to rotary kiln processing. As a result, additional thermal energy is required for moisture evaporation, leading to increased consumption of carbon-based fuels and reductants. This increased energy demand affects not only the overall energy balance of the process but also the reduction kinetics and thermal stability during the pre-reduction stage [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Recent studies have demonstrated the complexity of carbothermic reduction mechanisms in lateritic nickel ores, including selective reduction of nickel oxides, nucleation of metallic phases, and slag\u0026ndash;metal interactions under industrial conditions [\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. These processes strongly influence nickel enrichment efficiency and the final quality of ferronickel, which are highly dependent on temperature regime, reductant distribution, and reaction kinetics during both rotary kiln and electric furnace operation. The metallurgical performance of ferronickel is closely related to its chemical composition and microstructural homogeneity. Residual oxide phases and entrapped slag inclusions can adversely affect downstream refining processes and the quality of stainless steel products [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Furthermore, microstructural evolution during solidification governs the distribution of nickel within the iron-rich matrix, influencing alloy uniformity and performance [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAdvanced characterization techniques, particularly scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS), are widely used to investigate microstructural features and local elemental distribution in ferroalloys [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. These techniques allow identification of metallic matrices, oxide inclusions, and phase heterogeneities formed during large-scale smelting processes. Despite extensive global research, detailed microstructural investigations of industrial ferronickel produced under full-scale RKEF conditions in Southeast Europe remain limited. In particular, previous studies of the ferronickel plant in Drenas have mainly focused on process evaluation and material balance rather than detailed microstructural characterization [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The objective of this study is to provide a systematic microstructural and semi-quantitative chemical characterization of industrial ferronickel produced under real operating conditions, with emphasis on the relationship between process parameters, slag composition, and alloy quality.\u003c/p\u003e"},{"header":"2. MATERIALS AND METHODS","content":" \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. \u003cem\u003eIndustrial process and sampling\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eThe investigated material consisted of industrial ferronickel (Fe\u0026ndash;Ni) samples collected from a full-scale rotary kiln\u0026ndash;electric furnace (RKEF) production line processing lateritic nickel ores in Kosovo [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The analyzed material represents the final metallic product obtained after electric furnace smelting and subsequent refining in the converter. Samples were collected in granulated form under standard industrial operating conditions. Microstructural and chemical characterization was performed using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), widely applied for microstructural investigation and localized elemental analysis in ferroalloys [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Granulated ferronickel samples were examined in the as-received condition without chemical etching in order to preserve the original solidification morphology. Prior to analysis, selected particles were mounted and prepared for observation. SEM examinations were carried out under high-vacuum conditions using an accelerating voltage of 15\u0026ndash;20 kV. Both secondary electron (SE) and backscattered electron (BSE) imaging modes were employed to distinguish between metallic and oxide phases.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. \u003cem\u003eSlag sampling and chemical analysis\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eTo evaluate slag composition and metal losses during ferronickel production, industrial slag samples were also analyzed. A total of 31 slag samples obtained from electric furnace operation were considered. The amount of slag produced during individual operational periods ranged between approximately 788 t and 1502 t [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].The chemical composition of slag samples was determined using X-ray fluorescence (XRF) analysis in an industrial laboratory. The analyzed oxides included SiO₂, MgO, FeO, Al₂O₃, CaO and Cr₂O₃, together with nickel and total iron content. The slag composition is typical of lateritic nickel ore smelting systems and is characterized by a silicate-based matrix. Based on the collected operational data, the average slag composition is presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\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\u003eAverage chemical composition of industrial slag (wt.%)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eComponent\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eContent (wt.%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSiO₂\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e58.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFeO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMgO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e17.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAl₂O₃\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCaO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.38\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCr₂O₃\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.49\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.083\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFe (total)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e11.76\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=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. \u003cem\u003eMicrostructural characterization\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eMicrostructural characterization of ferronickel samples was performed using SEM in order to evaluate phase morphology, dendritic structures and the presence of non-metallic inclusions.\u003c/p\u003e \u003cp\u003eThe observations focused on identifying the metallic Fe\u0026ndash;Ni matrix, solidification features, and possible oxide inclusions formed during smelting and cooling. The use of EDS imaging enabled compositional contrast between metallic and oxide phases, facilitating phase identification.\u003c/p\u003e \u003cp\u003eMicrostructural characterization of ferronickel samples was performed using SEM in order to evaluate phase morphology, dendritic structures and the presence of non-metallic inclusions. A representative SEM micrograph of the investigated ferronickel is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. SEM micrograph of ferronickel (Fe\u0026ndash;Ni) with selected point EDS analysis indicating local elemental composition within the metallic matrix and inclusion regions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. \u003cem\u003eElemental analysis (EDS)\u003c/em\u003e\u003c/h2\u003e \u003cp\u003eThe local chemical composition of ferronickel samples was determined using EDS analysis attached to the scanning electron microscope. Measurements were performed at multiple selected micro-areas (\u0026ge;\u0026thinsp;10 points) within the metallic matrix to improve statistical representativeness.The analyzed elements included Fe, Ni, O and C. Representative EDS results indicate a metallic region composed mainly of iron (approximately 68.6 wt.%), with nickel present at about 5.5 wt.%. Oxygen (\u0026asymp;\u0026thinsp;21 wt.%) and carbon (\u0026asymp;\u0026thinsp;4\u0026ndash;5 wt.%) were also detected in localized regions, indicating the presence of oxide inclusions and residual carbon (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSemi-quantitative EDS analysis of a representative micro-area in industrial ferronickel (Fe\u0026ndash;Ni)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMap Sum Spectrum\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLine Type\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWeight %\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eWeight % Sigma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAtomic %\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eK series\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12.92\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eK series\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e43.54\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eK series\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e68.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e40.45\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eK series\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.09\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 EDS results presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e correspond to a localized micro-area within the ferronickel matrix and should therefore be considered semi-quantitative. The analysis indicates that iron is the dominant element, while nickel is present as the principal alloying component.\u003c/p\u003e \u003cp\u003eThe relatively high oxygen content suggests the presence of oxide inclusions or residual slag phases entrapped within the metallic matrix. Similarly, the detected carbon is attributed to carbothermic reduction processes and possible surface contamination during sample preparation. It should be noted that EDS analysis is sensitive to the analysed micro-volume and may not represent the bulk chemical composition of the ferroalloys (Fe-Ni).\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\u003eIndustrial production parameters of ferronickel obtained from electric furnace and converter operation\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePeriod 1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePeriod 2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePeriod 3\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNickel production (t)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e21.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e624.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5043.90\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNickel production (t/day)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e21.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e20.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e13.78\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNi content in ferronickel (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e17.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e18.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e18.51\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNickel recovery (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e100.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e98.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e86.49\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEnergy consumption (MWh)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1204.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e35997.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e318188.84\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecific energy consumption\u003c/p\u003e \u003cp\u003e(MWh/t Ni)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e55.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e57.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e63.08\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*Values above 100% may reflect uncertainties in industrial mass balance calculations and sampling variability\u003c/p\u003e \u003cp\u003eThe industrial data presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e indicate a progressive increase in specific energy consumption from 55.81 to 63.08 MWh/t Ni across the analyzed periods. This trend is accompanied by a decrease in nickel recovery from 98.17% to 86.49%, suggesting reduced process efficiency under later operating conditions.\u003c/p\u003e \u003cp\u003eThe increase in energy consumption may be associated with variations in ore quality, particularly moisture content and nickel grade, as well as changes in slag composition and furnace operating conditions. Higher FeO content in slag can indicate incomplete reduction, which is consistent with the oxygen-rich regions observed in the SEM\u0026ndash;EDS analysis.\u003c/p\u003e \u003cp\u003eThe nickel content in ferronickel remains relatively stable (17.7\u0026ndash;18.5 wt.%), indicating that alloy grade control is maintained despite fluctuations in process efficiency. However, the observed decline in recovery and increase in energy demand suggest that optimization of reduction conditions and slag chemistry could significantly improve overall metallurgical performance.\u003c/p\u003e \u003cp\u003eThe SEM micrograph (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) reveals a dendritic metallic structure typical of rapidly solidified ferronickel produced by the RKEF process. The heterogeneous morphology reflects non-equilibrium solidification conditions during tapping and granulation.\u003c/p\u003e \u003cp\u003eEDS point analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) confirms that the metallic matrix is primarily composed of iron with nickel distributed as the principal alloying element. However, the presence of oxygen detected in the analyzed micro-areas suggests the existence of oxide inclusions.\u003c/p\u003e \u003cp\u003eElemental mapping (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) provides further insight into phase distribution. Iron and nickel are relatively uniformly distributed within the metallic matrix, indicating effective alloy formation. In contrast, oxygen is localized in discrete regions, confirming the presence of oxide inclusions. Carbon appears in localized zones, which may be associated with residual carbon from carbothermic reduction or surface contamination.\u003c/p\u003e \u003cp\u003eThe presence of oxygen-rich inclusions is consistent with the industrial slag composition and the observed decrease in nickel recovery (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), suggesting incomplete slag\u0026ndash;metal separation and partial reduction of iron oxides during smelting.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. DISCUSSION","content":"\u003cp\u003eThe SEM micrograph (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) reveals a dendritic metallic structure typical of rapidly solidified ferronickel produced by the RKEF process. The heterogeneous morphology reflects non-equilibrium solidification conditions during tapping and granulation.\u003c/p\u003e \u003cp\u003eEDS point analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) confirms that the metallic matrix is primarily composed of iron with nickel distributed as the principal alloying element. However, the presence of oxygen detected in the analyzed micro-areas suggests the existence of oxide inclusions.\u003c/p\u003e \u003cp\u003eElemental mapping (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) provides further insight into phase distribution. Iron and nickel are relatively uniformly distributed within the metallic matrix, indicating effective alloy formation. In contrast, oxygen is localized in discrete regions, confirming the presence of oxide inclusions. Carbon appears in localized zones, which may be associated with residual carbon from carbothermic reduction or surface contamination.\u003c/p\u003e \u003cp\u003eThe presence of oxygen-rich inclusions is consistent with the industrial slag composition and the observed decrease in nickel recovery (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), suggesting incomplete slag\u0026ndash;metal separation and partial reduction of iron oxides during smelting.\u003c/p\u003e"},{"header":"4. CONCLUSIONS","content":"\u003cp\u003eBased on the obtained results, the following conclusions can be drawn:\u003c/p\u003e \u003cp\u003eIndustrial ferronickel produced via the RKEF process exhibits a heterogeneous dendritic microstructure typical of rapid solidification. SEM\u0026ndash;EDS analysis confirms that iron is the dominant element, with nickel relatively uniformly distributed within the metallic matrix. Oxygen-rich inclusions indicate incomplete slag\u0026ndash;metal separation and partial reduction, consistent with industrial slag composition.The increase in specific energy consumption and decrease in nickel recovery suggest reduced process efficiency under certain operating conditions. The study demonstrates that microstructural characteristics are directly influenced by process parameters, highlighting the importance of optimizing reduction conditions and slag chemistry.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eNo funding was received for this study.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eZ.B.-G. conceptualized the study and supervised the research. J.M. (corresponding author) designed the methodology, conducted the experimental work, performed the SEM\u0026ndash;EDS analysis, and prepared the figures. Z.B.-G. analyzed and interpreted the data. M.K.A. wrote the main manuscript text. All authors reviewed, revised, and approved the final version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cdiv class=\"Heading\"\u003e5. \u003cb\u003eREFERENCE\u003c/b\u003e\u003c/div\u003e \u003cli\u003e\u003cspan\u003eF.K. Crundwell, M.S. Moats, V. Ramachandran, T.G. Robinson, W.G. Davenport, \u003cem\u003eExtractive Metallurgy of Nickel, Cobalt and Platinum Group Metals\u003c/em\u003e (Elsevier, Oxford, 2011)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eC.K. Gupta, T.K. Mukherjee, \u003cem\u003eExtractive Metallurgy of Nickel, Cobalt and Platinum Group Metals\u003c/em\u003e (CRC, Boca Raton, 2007)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM.A. Rhamdhani, E. Jak, P.C. Hayes, Phase equilibria and slag\u0026ndash;metal reactions in nickel laterite smelting. Miner. Eng. \u003cb\u003e22\u003c/b\u003e, 311\u0026ndash;318 (2009)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eB. Tang, B. Li, H. Yang, Phase transformation in the metallic reduction process of laterite nickel ores. Metall. Res. Technol. \u003cb\u003e120\u003c/b\u003e, 291 (2023)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZ. Wang, L. Chen, Y. Zhang, Extraction of ferronickel concentrate by reduction roasting\u0026ndash;magnetic separation. Mater. Trans. \u003cb\u003e63\u003c/b\u003e, 1124\u0026ndash;1132 (2022)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJ. Zhang, Z. Wang, Y. Liu, High-grade ferronickel concentrates from laterite ore. Materials. \u003cb\u003e16\u003c/b\u003e, 7132 (2023)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZ. Bajraktari Gashi, B. Halilaj, Material balance of ferronickel production in Drenas. J. Technol. Exploit. Mech. Eng. \u003cb\u003e4\u003c/b\u003e, 29\u0026ndash;35 (2018)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eC. Rong, J. Zhang, Y. Li, Microstructural evolution of Fe\u0026ndash;Ni alloys during solidification. Mater. Charact. \u003cb\u003e128\u003c/b\u003e, 34\u0026ndash;42 (2017)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJ. Goldstein et al., \u003cem\u003eScanning Electron Microscopy and X-ray Microanalysis\u003c/em\u003e (Springer, New York, 2018)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA. \u0026Ouml;zg\u0026uuml;r, S. \u0026Ouml;zdemir, Microstructural characterization of ferronickel alloys using SEM\u0026ndash;EDS. J. Mater. Process. Technol. \u003cb\u003e299\u003c/b\u003e, 117285 (2021)\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Ferronickel, Lateritic ores, Microstructure, Pyrometallurgy, SEM-EDS, Stainless Steel","lastPublishedDoi":"10.21203/rs.3.rs-9561872/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9561872/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eFerronickel (Fe\u0026ndash;Ni) is a key ferroalloy used in stainless steel production, predominantly produced from lateritic ores via the rotary kiln\u0026ndash;electric furnace (RKEF) process. In this study, the microstructural features and localized chemical composition of industrial ferronickel produced in Kosovo were investigated using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS).The results reveal a heterogeneous metallic matrix with dendritic morphology, typical of rapid solidification under industrial conditions. SEM observations indicate the presence of non-metallic inclusions embedded within the Fe\u0026ndash;Ni matrix. EDS analysis confirms that iron is the dominant element, while nickel is relatively homogeneously distributed, suggesting effective alloying during smelting. Localized oxygen- rich regions are associated with oxide inclusions, likely originating from incomplete slag\u0026ndash;metal separation and residual oxides from the reduction process. The presence of carbon is attributed to carbothermic reduction in the rotary kiln stage. The results indicate that reduction reactions are advanced but not fully completed, which is consistent with industrial RKEF operation.\u003c/p\u003e \u003cp\u003eBy combining microstructural observations with industrial slag composition and process parameters, this study provides insight into the relationship between process conditions, inclusion formation, and alloy heterogeneity. The findings contribute to improved understanding of metallurgical efficiency and ferronickel quality in large-scale industrial production.\u003c/p\u003e","manuscriptTitle":"Microstructural and Chemical Characterization of Industrial Ferronickel Produced by the RKEF Process Using SEM–EDS Analysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-14 07:19:56","doi":"10.21203/rs.3.rs-9561872/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"17cd8026-3c2f-42cb-ba56-ad1feec17c12","owner":[],"postedDate":"May 14th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-05-14T07:19:56+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-14 07:19:56","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9561872","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9561872","identity":"rs-9561872","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}