Self-lubricating properties of carbon filled oblique angle deposition porous TiN coating

Self-lubricating properties of carbon filled oblique angle deposition porous TiN coating | 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 Self-lubricating properties of carbon filled oblique angle deposition porous TiN coating Kai Le, Ke Li, Yuzhen Liu, Huijie Zhang, Lina Gao, Yong Luo, Shusheng Xu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6358874/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 To address the issue of easy removal of lubricant phase by frictional behaviors, this study provided an innovative approach to fabricate porous TiN-based coatings subsequently filled by lubricants carbon. The process commenced with oblique angle deposition of porous TiN coatings, creating reservoir to store the carbon lubricants. The mechanical performance, pore size, and porosity can be adjusted through changing deposition gas pressure. The hardness increases from 12.64 to 20.36 GPa, and the pore size decreases, but the porosity increases from 7.5–13.7% with rising working pressure from 0.27 to 0.8 Pa. Then, the carbon was filled into the pore of porous TiN through sequential hydrothermal carbonization and thermal treatment. The friction test results show that the carbon filled porous TiN coating deposited at 0.8 Pa possesses the excellent tribological performance, maintaining the friction coefficient below 0.4 for 8,100 s, which exceeds the ~ 3,000 s of coating deposited at sputtering pressure of 0.27 Pa. There is no doubt that tribological performance of carbon filled porous TiN coatings are better than non-oblique angle deposited TiN-C coatings (µ ≈ 0.85 at 1,200 s). This coating also exhibits excellent wear resistance with a very low wear rate of 6.9 × 10 − 7 mm 3 /N⋅m. The wear mechanism originated from continuous carbon release from pore TiN reservoirs to the wear interface, maintaining lubricating carbon films during sliding contact. Oblique angle deposition porous TiN coating carbon reservoir 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 1. Introduction Friction and wear are the ubiquitous phenomenon that has diverse implications in many technological fields, which are often the core cause of the energy loss and parts damage [ 1 – 3 ]. Hence, there persists a relentless pursuit to reduce the coefficient of friction and diminish wear between mechanical components [ 4 , 5 ]. Solid lubricants, especially the carbon materials and transition metal disulfides, with their unique physical and chemical properties, have become an ideal solution to meet lubrication challenges in harsh environments and special working conditions, such as the high/low temperature environment, vacuum, and electrical condition [ 6 – 8 ]. However, solid lubricants face the problem of being easily removed by the friction force due to their easy shearing properties. Some efforts have been made to keep the solid lubricants on the friction interface. Among them, surface texturing technology has been widely regarded as the efficient way to improve the tribological performance of solid lubricants [ 9 – 11 ]. Almost all relevant studies confirm that the surface texture serves as a reservoir to enhance lubricant retention and as a trap to capture wear debris [ 12 , 13 ]. However, the rough surface rough surface of the surface texturing limits its application in precision equipment. Moreover, it is difficult to prepare a uniform texture on the hard materials, which usually have excellent wear resistance. For example, hard coatings prepared by physical vapor deposition (PVD) technology, including TiN, CrN, CrAlN, etc., are hard coatings with excellent wear resistance that are widely utilized in industry [ 14 – 16 ]. PVD TiN coating is one of the most established engineering materials, which has a wide range of technical applications. It has long been employed as the protective coating in mold manufacturing, the automotive industry, aerospace, and other fields [ 17 – 19 ]. Interestingly, the PVD TiN coating tends to grow in columnar during the deposition, which provides a way to produce porous TiN coating [ 20 ]. Over the past 30 years, porous TiN coatings have been widely reported using the oblique angle deposition (OAD) technology, which is a special technique in PVD by inclining the substrate surface [ 21 – 23 ]. When deposited the TiN coatings by OAD, the obtained TiN coatings would acquire the structure of inclined nano-columns separated by intercolumnar porosity, due to the influence of the shadowing effect.[ 24 ] The inclination angle of the substrate affects shadowing effect, thereby influencing the porosity between the columns [ 21 , 25 , 26 ]. Due to the porous structure, OAD TiN coatings have been systematically applied in the fields such as sensor technology, electrochemistry, and catalysis [ 23 , 27 , 28 ]. More interestingly, when it used as the friction pair, the pores in the OAD TiN can act as reservoir for storing and retaining solid lubricants. Herein, porous TiN coating filled with lubricant carbon has been successfully prepared. The porous TiN coating was firstly prepared using OAD technology, and the effect of deposition gas pressure on the pore structure and mechanical properties of the coating was investigated. Then, carbon was embedded into the pores of TiN coating as solid lubricant through hydrothermal carbonization and heat treatment. The porous OAD TiN coating exhibits excellent storage and retention capabilities for lubricant carbon, and the lubricant carbon could be released from the pores to the sliding interface and reduce the friction as well as wear. The OAD TiN coating deposited at 0.8 Pa possessed a hardness of 20.36 GPa and a porosity of 13.7%, and it possesses the excellent tribological properties as carbon filling. It maintained a friction coefficient of below 0.4 for 8,100 s under a normal load of 2 N (the contact pressure of 0.89 GPa) and had a very low wear rate of 6.9×10 − 7 mm 3 /N⋅m. Obviously, it provides a novel way for the design of high-performance lubricating coating. 2. Experimental method 2.1 Preparation of coatings All the coatings were deposited by using the arc ion plating technique. The stainless steel (SS 304) with the mirrored surface in rectangular size (20 mm×20 mm×5 mm) were applied as the substrate. The distance between Ti target and substrate is approx. 400 mm, and the depositions were carried out at 200 ℃. Before the deposition, the surface of substrate was further cleaned by Ar ion bombardment under the bias voltage of -1,200 V and Ar pressure of 1.0 Pa. Subsequently, to improve the surface activity and adhesion, a Ti sublayer was deposited at bias voltage of -200 V and sputtering Ar pressure of 0.5 Pa. Details of the preparation parameters of the TiN film are listed in Table 1 . Two porous OAD-TiN coatings were deposited at the sputtering N 2 pressure of 0.27 and 0.8 Pa with the inclination angle of 80°, which were designated as OT 0.27 and OT 0.8 coatings, respectively. As a contrast, a reference TiN coating with fully dense microstructure was also deposited at sputtering N 2 pressure of 0.8 Pa without inclination angle, namely as DT coating. Table 1 Preparation parameter of the TiN film Item Parameter Deposition temperature 200 ℃ Working pressure 0.27 and 0.8 Pa Arc current 80 A Arc voltage 17 V Deposition time 30 min Inclination angle 0 ° and 80 ° The as-prepared TiN coatings were placed into 1 M glucose solution and then sealed in a Teflon-lined stainless-steel autoclave to heat at 180 ℃ for 3 h. After the reaction treatment, samples were washed and dried at 60 ℃ for 12 h. Then, the samples were heat at 500 ℃ for 3 h at Ar atmosphere to get carbon filled coatings. The DT, OT 0.27 and OT 0.8 coatings were designated as DTC, OTC 0.27 and OTC 0.8 after the coatings were filled with carbon. Figure 1 depicts the schematic diagram of the preparation process of composite coatings. 2.2 Characterization of coatings The surface and cross-sectional feature of the coatings were measured by using the scanning electron microscopy (SEM FEI Quanta FEG 250) equipped with EDS (Oxford, XMax). X-ray diffraction (XRD, D/MAX-RB, Rigaku, Japan) in grazing incident mode was used to characterize the crystalline structure of coatings at an incident angle of 1.5 °. Raman spectroscopy (DXR2, Thermo, USA) was performed on the surface after carbon filling. Nanoindenter (Step E400, Anton Paar, Austria) was used to perform the mechanical properties of TiN coatings. The adhesion of the coatings was determined by using automatic scratch teste (MFT-4000, Huahui, China). The applied load was increased from 0 to 50 N at a loading speed of 50 N/min. After the scratch test, the scratch tracks were observed by microscopes (Axio Image, ZEISS, Gemany). 2.3 Friction test Friction measurements were carried out on the planar surface of coating by using a ball-on-disk rotary tribometer. Measurements were made in ambient air at ~ 32% relative humidity environments and room temperature. In the sliding process, a Al 2 O 3 ball of 8 mm in diameter was used as friction pairs, with a rotation speed of 200 rpm, rotation radius of 4 mm and normal load of 2 N. After friction test, the white light interferometry 3D profiler (MicroXAM-800, KLA-Tencor, USA) and Raman spectroscopy were carried out to analyze the wear tracks. 3. Results and discussion The structure of as-prepared TiN coatings was firstly investigated by SEM, as given in Fig. 2 . Obviously, the DT coating shows dense and smooth surface (Fig. 2 a ) , and both the OT 0.27 and OT 0.8 coatings present crack-like pore structure(Fig. 2 b, c). It should be noted that the pores in OT 0.8 coating is smaller and the structure is denser than OT 0.27 coating. The porosity of coatings was estimated by using an image processing program (Image J) from the SEM pictures.[ 29 , 30 ] The porosity of OT 0.27 and OT 0.8 coatings are about 7.5% and 13.7%, indicating that OT 0.8 coating may possess the more space to store solid lubricants. Furthermore, the cross-section morphology of the coatings was also investigated. In Fig. 2 d, the DT coating displays dense structure morphology. In comparison, the cross-section images reveal the obvious columnar structure for the OT 0.27 and OT 0.8 coatings. At the extreme inclination angle of over 80° for deposition, the shadowing effect dominates the mobility and diffusion of adatoms, result in forming porous and titled nanocolumns [ 31 , 32 ]. The columnar structure of OT 0.27 coating (Fig. 2 e) is not clear, while the OT 0.8 coatings (Fig. 2 f) exhibits more uniform and smaller columnar structure. It can be ascribed to that more collisions generally occur at higher sputtering pressures, which limits the lateral mobility of atom, resulting in vertical columnar growth [ 33 – 35 ]. Thus, TiN column of OT 0.8 coating possess the obvious boundaries, with width of 160 nm and uniform height. As a result, the OT 0.8 coating shows uniform pores and flat surface. The average tilt angle of TiN columns in OT 0.8 coating remain at a low value of 12°. Apparently, porous TiN coatings prepared by cathodic arc evaporation could serve as the reservoir for lubricants. Table 2 Indentation hardness (H) and elastic modulus (E) of deposited TiN coatings. Coatings HIT (GPa) E (GPa) DT 29.98 412.73 OT 0.8 20.36 271.87 OT 0.27 12.64 196.82 The mechanical properties of all coatings were investigated by using the nanoindenter, and the results of hardness (H) and elastic modulus (E) are listed in Table 2 . The maximum penetration depth ( h max ) is less than 0.1 d ( d = film thickness) [ 36 ]. The H and E values of DT coating are 29.98 GPa and 412.73 GPa, which are much higher than OAD TiN coatings. This result indicates that tilted column and pore in coatings would decrease the mechanical performances, which may subsequently affect the tribological properties. Furthermore, the deposition pressure significantly affected the mechanical properties of OAD TiN coatings. The H and E values of OT 0.27 coating are only 12.64 GPa and 196.85 GPa, which are lower than those of OT 0.8 coating. It can be attributed to that the OT 0.8 coating has more uniform columnar structure, smaller tilt angle and pore size. The scratch test results demonstrate that adhesion of OT 0.8 coating is 34.1 N, a little bit higher than OT 0.27 coating. Due to tilted columnar and porous structure, the adhesion of both OAD TiN coatings are lower than dense DT coating (37.9 N). Thus, according to the abovementioned characterization results, OT 0.8 coating is selected as the candidate for subsequent study. The crystalline structure of the DT, OT 0.8 , and carbon filled coatings (OTC 0.8 ) were investigated by XRD and the patterns are given in Fig. 4 a. In low angle diffraction part, all the coatings show five peaks, corresponding to the (111), (200), (220), (311) and (222) plane of face-centered cubic (FCC) TiN [ 37 ]. In comparison, the DT coating shows a (111) preferred orientation, while the OT coatings present a (220) preferred orientation. It can be ascribed to the fact that the vertical direction energy of the particles decreases as the substrate tilt angle increases, leading to a lower momentum of the particles bombarding the coating [ 22 ]. As a result, the intrinsic stress of the OT coating should be lower than DT coating because the coating stress is determined by particle momentum [ 38 , 39 ]. Thus, the OAD weakens the (111) orientation that always occur under high stress and displays (220) preferred orientation.[ 40 ] It should be noticed that the intensity of (200) peak increases in OTC 0.8 coating, which is attributed to heat treatment after hydrothermal carbonization. The (220) plane has the lowest surface energy in the FCC TiN crystal, which is contributed to improve the wear resistance and adhesion [ 41 – 43 ]. The carbon species produced by hydrothermal carbonization treatment are usually amorphous, which cannot be detected by XRD measurement [ 44 ]. Therefore, Raman spectroscopy was used to characterize the coating. Figure 4 b shows the Raman spectrum of OTC 0.8 coating. The spectrum shows typical carbon peaks at 1370 and 1596 cm − 1 , corresponding to D and G peaks [ 45 , 46 ]. The roughness of DT and OT 0.8 coatings was investigated by AFM. As it shown in Fig. 5 , OT 0.8 coatings possesses the lower roughness ( Ra of 194 nm) than DT coating ( Ra of 251 nm). Nikhil et al. reported that the TiN with a predominant (200) orientation had a considerably smoother surface than the one with (111) orientation, which is consistent with the XRD results of OT 0.8 coating [ 47 ]. The cross-sectional morphology of the OTC 0.8 coating was also investigated, and the SEM images are displayed in Fig. 6 . It can be seen that the coating becomes dense and the columnar structure can still be observed (Fig. 6 a). However, the columns became more vertical after the hydrothermal treatment, which is beneficial for improvement of the adhesion of coatings. The scratch test reveals that the adhesion of OTC 0.8 coating on stainless steel substrate increases to 38.4 N (Fig. 7 ). Furthermore, the carbon layer with thickness of 50 nm is covering on the OTC 0.8 coating surface, as shown in Fig. 6 b. To clarify that the carbon was successfully filled into the pores of the OTC 0.8 coating, EDS measurement was employed. As it shown in Fig. 8 , the signal of element C is sI intensive in the cross-section of OTC 0.8 coating, while it is weak for DTC coating. Thus, it can be demonstrated that the hydrothermal carbonization treatment can fill the carbon into the pores of OAD-TiN coating. The tribological performance of OTC 0.8 coatings was investigated by using home-made ball-on-disc tribometer at normal load of 2 N and rotation speed of 200 rpm. For comparison, the tribological performance of OT 0.8 coating was also measured, and the frictional coefficient curves are presented in Fig. 9 a. It can be observed that the friction coefficient of OT 0.8 coating is very high and it can be worn out after sliding of 850 s. Notably, the OTC 0.8 coating maintains a low friction coefficient below 0.4 for ~ t 2.25 h (Fig. 9 b). The tribological performance is also much better than that of DTC coating with initial COF of 0.3 for 1200 s and sequent COF over 0.85 ( Fig. S1 ). The initial low friction can be attributed to the lubricant carbon layer at the top of DT coating. However, this carbon layer can be easily removed by the friction behavior, leading to the increase in friction. Furthermore, the tribological performance of OTC 0.27 coating was also evaluated as shown in Fig. S2 . In the initial 2,500 s sliding, the friction coefficient of OTC 0.27 coating is similar to the OTC 0.8 coating. Then, the friction coefficient of OTC 0.27 coating starts to increase and reaches up to 0.6 at 6,000 s. It is proved that the tribological performance of OTC 0.27 coating is inferior to the OTC 0.8 coating but much superior to DTC coating. The wear behavior of OT 0.8 and OTC 0.8 coatings after sliding friction of 900 s was evaluated. Figures 9 c,d present the 3D morphologies and corresponding cross-sectional topography of the wear tracks of OT 0.8 and OTC 0.8 coatings, respectively. The OT 0.8 coating has severe wear, with the depth of the wear track of 4.30 µm, which is higher than the thickness of OT 0.8 coating (~ 2 µm), suggesting its worn out. As carbon component incorporated in the porous TiN coating, the OTC 0.8 coating possesses outstanding wear resistance with slight 0.22 µm depth wear track. The wear rate of OTC 0.8 is 6.9 × 10 − 7 mm 3 /N⋅m, one of thirtieth of that of OT 0.8 (Fig. 9 e). It can be stated the combination strategy of fabrication of porous hard TiN coating and incorporation of lubricant carbon into the pores can significantly reduce the friction as well as wear behaviors. To further elucidate the friction and wear mechanism, the optical microscopy and Raman spectroscopy measurement were conducted to analyze the sliding interface. Figures 10 and 11 display optical images and Raman spectra on the wear track of OTC 0.8 and DTC coatings after sliding friction different time, respectively. The initial surfaces of both as-prepared coatings are coated by the carbon layer (Fig. 10 a and Fig. 11 a), which show strong peak intensity of D and G bands (Fig. 10 e and Fig. 11 c). After sliding friction for 1 h, the optical image of OTC 0.8 coating shows a bright wear track covered with discontinuous dark carbon films that can play the dominant role in reducing the friction (Fig. 10 b). The friction behavior presents the high and fluctuant characteristics of COF of 0.35 ~ 0.40, due to the insufficient lubricant carbon film covering on the wear track surface. The weak D and G band Raman peaks in the bright region demonstrate the superior bearing capacity of porous TiN coating and reservoir and self-releasing features of lubricant carbon from the pores of the OT 0.8 coating. In contrast, for the DTC coating, the bright TiN has been fully exposed after sliding friction for 1 h, and the Raman spectrum shows no lubricant carbon presentation (Fig. 11 b). The wear track characteristics of the OTC 0.8 coating after testing for 2 h show a similar phenomenon to that of 1 h (Fig. 10 c). These results demonstrate that the carbon stored in the OT 0.8 coating can be released to the sliding interface driven by the friction behaviors to reduce the friction as well as wear. Nevertheless, due to the pretty limited storage and supply amount of the lubricant carbon in the interior of the porous TiN based coating, the friction coefficient is relatively high but still much lower than pure TiN (such as DT and OT 0.8 coatings). Finally, after the carbon lubricant is completely released and consumed, the friction coefficient rapidly increases and the coating can be worn out, resulting in the fully exposure of the 304 substrate (Fig. 10 d). On the abovementioned, the friction and wear mechanism of the DTC and OTC 0.8 coatings can be illustrated in Fig. 12 . Both surfaces of the DTC and OTC 0.8 coatings were covered by lubricant carbon layer after the hydrothermal carbonization treatment. In the initial sliding friction stage, the recombined lubricant film originating from the surface carbon layer on wear track driven by friction behaviors can reduce the friction as well as wear. Thus, both the DTC and OTC 0.8 coatings show a low friction coefficient of 0.2 at the initial 200 s sliding friction stage. As the sliding friction ongoing, the lubricant carbon film on the wear track of DTC coating is completely consumed, resulting in the full exposure of the TiN layer and increase in the friction (Fig. 12 a). Beneficial from the reservoir and self-releasing feature of lubricant carbon in the porous TiN coating, the recombined lubricant carbon film on the wear track surface driven by frictional behaviors can be maintained for long-terms. Thus, the robust friction reduction and high wear resistance was achieved. (Fig. 12 b). After this long steady friction stage, due to the limit amount of lubricant carbon in the reservoirs of the porous TiN coating, the formed carbon film become discontinuous, thereby, the friction coefficient slowly increases to 0.4. At this stage, the removal and formation of lubricant carbon film driven by friction behaviors achieve a balance. The lubricant performance failed as the interior carbon was fully released and consumed during friction process. Then, the OTC 0.8 coating evolved into the high friction level as the lubricant was absent. 4. Conclusion In this study, the porous TiN coating was prepared by depositing the porous TiN coating via the oblique angle deposition technique, the lubricant carbon was then filled into the interior of the porous TiN by a combination of hydrothermal carbonization and heat treatment. The porous TiN coating acts as not only a load-bearing layer and the reservoir to store the carbon lubricant, which can release carbon to the sliding interface driven by friction behanviors, thus significantly reducing the friction and wear during sliding. Morphology and mechanical properties characterizations demonstrate that the porous TiN coating deposited at 0.8 Pa with an oblique angle of 80° possesses better mechanical properties, more uniform pores and higher porosity than the coating deposited at 0.27 Pa, suggesting the better capacities to bear the load and store the carbon. As a result, the friction coefficient of OTC 0.8 coating can be maintained below 0.4 for ~ 8,100 s, longer than the ~ 3,000 s of OTC 0.27 coating. Notably, both the OTC coatings are better than the DTC coatings, which reaches a high friction coefficient of 0.85 at ~ 1,200 s. Moreover, OTC 0.8 coating also possesses a low wear rate of 6.9×10 − 7 mm 3 /N⋅m. The excellent tribological performance of OTC coating demonstrates that the oblique angel deposition of hard porous coatings to store the lubricants offers a novel strategy to design the lubricating coatings. Declarations Author Contribution Kai Le: investigation, visualization, data curation, funding acquisition, and writing of the original draft. Ke li: investigation , methodology, data curation. Yuzhen Liu: revision of the manuscript. Huijie Zhang and Lina Gao: data curation. Yong Luo: supervision and revision of the manuscript. Shusheng Xu: conceptualization, methodology, funding acquisition, supervision, and revision of the manuscript. Acknowledgements The authors are grateful for the financial support provided by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB0470102), the Natural Science Foundation of Shandong Province (No. 2022HWYQ-096), the Scientific Instrument Development Program of the Chinese Academy of Sciences (No. PTYQ2024YZ0006), the Key Instrument Development Program of the National Natural Science Foundation of China (No. 52427807), the Key Research Project of Shandong Provincial Natural Science Foundation (No. ZR2023ZD13), the Key Research and Development Program in Shandong Province (No. SYS202203), the Key Research Project of Shandong Provincial Natural Science Foundation (No. 2024KJHZ017), and the Program for Taishan Scholars of Shandong Province. References Chen, H., Wang, W., Le, K., Liu, Y., Gao, X., Luo, Y., et al.: Effects of substrate roughness on the tribological properties of duplex plasma nitrided and MoS 2 coated Ti6Al4V alloy. Tribol Int. 191 , 109123 (2024) Liu, Y., Han, J.-H., Xu, S., Jung, Y.C., Kim, D.-E.: Dual in-situ observation of tribochemical and morphological evolution of single-layer WS 2 and multi-layer WS2/C coatings. Friction. 12 , 1580–1598 (2024) Liu, R., Zhang, Y., Pu, J., Jie, M., Xiong, Q., Zhang, X., et al.: Wear Mechanism and Wear Debris Characterization of ULWPE in Multidirectional Motion. Tribol Lett. 72 , 130 (2024) Dohda, K., Boher, C., Rezai-Aria, F.: Mahayotsanun, N. Tribology in metal forming at elevated temperatures. Friction. 3 , 1–27 (2015) Liu, J., Yan, Z., Hao, J., Liu, W.: The influence of proton radiation on the friction and wear of Ti:WS 2 /P201 composite lubricating materials for space application. Wear. 538–539 , 15 (2024) Liu, Y., Le, K., Han, J.-H., Teng, H., Xiu, Z., Jung, C.: Understanding the influence of carbon interlayers on material removal and tribochemical evolution in multilayer coatings through In-Situ analysis. Carbon. 230 , 119593 (2024) Liu, X., Le, K., Wang, J., Lin, H., Liu, Y., Jiang, F., et al.: Synergistic lubrication of multilayer Ti 3 C 2 T x @MoS 2 composite coatings via hydrothermal synthesis. Appl. Surf. Sci. 668 , 160400 (2024) Xu, S., Sun, J., Weng, L., Hua, Y., Liu, W., Neville, A., et al.: In-situ friction and wear responses of WS 2 films to space environment: Vacuum and atomic oxygen. Appl. Surf. Sci. 447 , 368–373 (2018) Ripoll, M.R., Simič, R., Brenner, J., Podgornik, B.: Friction and lifetime of laser surface–textured and MoS 2 -Coated Ti6Al4V under dry reciprocating sliding. Tribol Lett. 51 , 261–271 (2013) Bao, Y., Deng, J., Wang, J., Wang, R., Sun, Q., Wu, J.: Tribological properties of Bi 2 S 3 /MoS 2 composite coatings deposited on biomimetic leaf vein textured surfaces. Tribol Lett. 71 , 97 (2023) Narayana, T., Saleem, S.S.: Enhancing fretting wear behavior of Ti64 alloy: The impact of surface textures and CrN-MoS 2 -Ag composite coating. Tribol Int. 193 , 109346 (2024) Zhang, Z., Deng, J., Wang, R., Bao, Y., Dou, Z., Tang, X.: Wear Performance of Electro-Fluid Mask In Situ Forming TiO 2 -MoS 2 Alternate Coatings Under Different Friction Conditions. Tribol Lett. 72 , 28 (2024) Feng, X., Wang, R., Wei, G., Zheng, Y., Hu, H., Yang, L., et al.: Effect of a micro-textured surface with deposited MoS 2 -Ti film on long-term wear performance in vacuum. Surf. Coat. Technol. 445 , 128722 (2022) Fu, X., Cao, L., Qi, C., Wan, Y., Xu, C.: Ultralow friction of PVD TiN coating in the presence of glycerol as a green lubricant. Ceram. Int. 46 , 24302–24311 (2020) Alkan, S., Gök, M.S.: Influence of plasma nitriding pre-treatment on the corrosion and tribocorrosion behaviours of PVD CrN, TiN and AlTiN coated AISI 4140 steel in seawater. Lubr Sci. 34 , 67–83 (2022) Tiwari, S.K., Rao, A.U., Kharb, A.S., Avasthi, D.K., Verma, P.C., Chawla, A.K.: The effect of sputtering parameters and doping on the properties of CrN-based coatings—A critical review. Surf. Interface Anal. 56 , 479–497 (2024) Panjan, P., Drnovšek, A., Terek, P., Miletić, A., Čekada, M., Panjan, M.: Comparative study of tribological behavior of TiN hard coatings deposited by various PVD deposition techniques. Coatings. 12 , 294 (2022) Chowdhury, M., Bose, B., Yamamoto, K., Shuster, L., Paiva, J., Fox-Rabinovich, G., et al.: Wear performance investigation of PVD coated and uncoated carbide tools during high-speed machining of TiAl6V4 aerospace alloy. Wear. 446 , 203168 (2020) Alfath, S.A., Ponte, F., Sharma, P., Ferreira, F., Laranjeira, J., Carvalho, S., et al.: PVD decorative coatings on polycarbonate and polyamide substrates for the automotive industry. Surf. Interfaces. 52 , 104887 (2024) Mareus, R., Mastail, C., Anğay, F., Brunetière, N., Abadias, G.: Study of columnar growth, texture development and wettability of reactively sputter-deposited TiN, ZrN and HfN thin films at glancing angle incidence. Surf. Coat. Technol. 399 , 126130 (2020) Jhajhria, D., Tiwari, P., Chandra, R.: Planar microsupercapacitors based on oblique angle deposited highly porous TiN thin films. ACS Appl. Mater. Interfaces. 14 , 26162–26170 (2022) Bouaouina, B., Mastail, C., Besnard, A., Mareus, R., Nita, F., Michel, A., et al.: Nanocolumnar TiN thin film growth by oblique angle sputter-deposition: Experiments vs. simulations. Mater. Des. 160 , 338–349 (2018) Naas, L.-A., Bouaouina, B., Bensouici, F., Mokeddem, K., Abaidia, S.E.: Effect of TiN thin films deposited by oblique angle sputter deposition on sol-gel coated TiO 2 layers for photocatalytic applications. Thin Solid Films. 793 , 140275 (2024) Mareus, R., Mastail, C., Nita, F., Michel, A., Abadias, G.: Effect of temperature on the growth of TiN thin films by oblique angle sputter-deposition: A three-dimensional atomistic computational study. Comp. Mater. Sci. 197 , 110662 (2021) Hawkeye, M.M., Brett, M.J.: Glancing angle deposition: Fabrication, properties, and applications of micro-and nanostructured thin films. J. Vac Sci. Technol. A. 25 , 1317–1335 (2007) Sadeghi-Khosravieh, S., Robbie, K.: Morphology and crystal texture in tilted columnar micro-structured titanium thin film coatings. Thin Solid Films. 627 , 69–76 (2017) Marques, S., Carvalho, I., Henriques, M., Polcar, T., Carvalho, S.: PVD-grown antibacterial Ag-TiN films on piezoelectric PVDF substrates for sensor applications. Surf. Coat. Technol. 281 , 117–124 (2015) Pedrosa, P., Machado, D., Fiedler, P., Vasconcelos, B., Alves, E., Barradas, N.P., et al.: Electrochemical characterization of nanostructured Ag: TiN thin films produced by glancing angle deposition on polyurethane substrates for bio-electrode applications. J. Electroanal. Chem. 768 , 110–120 (2016) Jen, Y.-J., Wang, W.-C., Wu, K.-L., Lin, M.-J.: Extinction properties of obliquely deposited TiN nanorod arrays. Coatings. 8 , 465 (2018) AlMarzooqi, F.A., Bilad, M., Mansoor, B., Arafat, H.A.: A comparative study of image analysis and porometry techniques for characterization of porous membranes. J. Mater. Sci. 51 , 2017–2032 (2016) Robbie, K., Sit, J., Brett, M.: Advanced techniques for glancing angle deposition. J. Vac Sci. Technol. B. 16 , 1115–1122 (1998) Buzea, C., Kaminska, K., Beydaghyan, G., Brown, T., Elliott, C., Dean, C., et al.: Thickness and density evaluation for nanostructured thin films by glancing angle deposition. J. Vac Sci. Technol. B. 23 , 2545–2552 (2005) Meese, W.J., Lu, T.-M.: Scaling behavior of columnar structure during physical vapor deposition. J. Appl. Phys. 123 , 075302 (2018) Mazor, A., Srolovitz, D., Hagan, P., Bukiet, B.G.: Columnar growth in thin films. Phys. Rev. Lett. 60 , 424 (1988) Drüsedau, T., Löhmann, M., Klabunde, F., John, T.-M.: Investigations on energy fluxes in magnetron sputter-deposition: implications for texturing and nanoporosity of metals. Surf. Coat. Technol. 133 , 126–130 (2000) Jönsson, B., Hogmark, S.: Hardness measurements of thin films. Thin solid films. 114 , 257–269 (1984) Yang, J., Le, K., Chen, H., Zhao, X., Xie, X., Luo, Y., et al.: The significantly enhanced mechanical and tribological performances of the dual plasma nitrided and PVD coated Ti6Al4V alloy. Int. J. Precis Eng. Man. 24 , 607–619 (2023) Windischmann, H.: Intrinsic stress and mechanical properties of hydrogenated silicon carbide produced by plasma-enhanced chemical vapor deposition. J. Vac Sci. Technol. A. 9 , 2459–2463 (1991) Chou, W.-J., Yu, G.-P., Huang, J.-H.: Mechanical properties of TiN thin film coatings on 304 stainless steel substrates. Surf. Coat. Technol. 149 , 7–13 (2002) Abadias, G., Tse, Y., Guérin, P., Pelosin, V.: Interdependence between stress, preferred orientation, and surface morphology of nanocrystalline TiN thin films deposited by dual ion beam sputtering. J. Appl. Phys. 99 , 113519 (2006) Oh, U., Je, J.H.: Effects of strain energy on the preferred orientation of TiN thin films. J. Appl. Phys. 74 , 1692–1696 (1993) Jones, M., McColl, I., Grant, D.: Effect of substrate preparation and deposition conditions on the preferred orientation of TiN coatings deposited by RF reactive sputtering. Surf. Coat. Technol. 132 , 143–151 (2000) Diserens, M., Patscheider, J., Levy, F.: Improving the properties of titanium nitride by incorporation of silicon. Surf. Coat. Technol. 108 , 241–246 (1998) Yu, S., He, J., Zhang, Z., Sun, Z., Xie, M., Xu, Y., et al.: Towards negative emissions: Hydrothermal carbonization of biomass for sustainable carbon materials. Adv. Mater. 36 , 2307412 (2024) Li, Y.-S., Jang, S., Khan, A.M., Martin, T.V., Ogrinc, A.L., Wang, Q.J., et al.: Possible origin of D-and G-band features in Raman spectra of tribofilms. Tribol Lett. 71 , 57 (2023) Hashizume, N., Yamamoto, Y., Chen, C., Tokoroyama, T., Zhang, R., Diao, D., et al.: The Effect of Carbon Structure of DLC Coatings on Friction Characteristics of MoDTC-Derived Tribofilm by Using an In Situ Reflectance Spectroscopy. Tribol Lett. 72 , 30 (2024) Ponon, N.K., Appleby, D.J., Arac, E., King, P., Ganti, S., Kwa, K.S., et al.: Effect of deposition conditions and post deposition anneal on reactively sputtered titanium nitride thin films. Thin Solid Films. 578 , 31–37 (2015) Additional Declarations No competing interests reported. Supplementary Files SupplementalMaterials.docx 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-6358874","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":438357231,"identity":"b5e4d32d-1baa-429d-8ddd-57179f196693","order_by":0,"name":"Kai Le","email":"","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Kai","middleName":"","lastName":"Le","suffix":""},{"id":438357232,"identity":"a3771114-457b-4366-baf3-76b22bcfc44c","order_by":1,"name":"Ke Li","email":"","orcid":"","institution":"China University of Mining and Technology","correspondingAuthor":false,"prefix":"","firstName":"Ke","middleName":"","lastName":"Li","suffix":""},{"id":438357233,"identity":"e624c468-e9e4-433d-9af5-afa9cffff351","order_by":2,"name":"Yuzhen Liu","email":"","orcid":"","institution":"Yonsei University","correspondingAuthor":false,"prefix":"","firstName":"Yuzhen","middleName":"","lastName":"Liu","suffix":""},{"id":438357234,"identity":"7bc54b16-079a-4f8e-b03a-503987ee0d11","order_by":3,"name":"Huijie Zhang","email":"","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Huijie","middleName":"","lastName":"Zhang","suffix":""},{"id":438357235,"identity":"a3c48fe1-c56c-47af-9b07-f367305f0424","order_by":4,"name":"Lina Gao","email":"","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Lina","middleName":"","lastName":"Gao","suffix":""},{"id":438357236,"identity":"32c38055-8f6d-43c8-8fe3-386e317346f5","order_by":5,"name":"Yong Luo","email":"","orcid":"","institution":"China University of Mining and Technology","correspondingAuthor":false,"prefix":"","firstName":"Yong","middleName":"","lastName":"Luo","suffix":""},{"id":438357237,"identity":"f16a068f-c83b-471b-93b1-292d928fca55","order_by":6,"name":"Shusheng Xu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAq0lEQVRIiWNgGAWjYLCCDwUSJOpgnGFAqhZmHgNSlMv3nzGTtjGwkDdnYH748QeDXR5BLQY30tKkcwwkDHc2sBlL8zAkFxPWIsF8DKQlweAAD4M0A8OBxAbCDjvYJm0B0cL88wcxWhgOJB+TZoBoYZPgIUYL0C/Jlj0gvzSzmVnzGCQT47Azhjd+VNTJm7M3P775o8KOCIfBrWMGk0SrJ1XxKBgFo2AUjCwAACxgMHdUt2A5AAAAAElFTkSuQmCC","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":true,"prefix":"","firstName":"Shusheng","middleName":"","lastName":"Xu","suffix":""}],"badges":[],"createdAt":"2025-04-02 07:53:31","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-6358874/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6358874/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":80055330,"identity":"7e21f84e-cd96-49ac-8b1b-eddab8409530","added_by":"auto","created_at":"2025-04-07 11:17:01","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":28476,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic illustration of the preparation process of composite coatings by arc ion plating, hydrothermal carbonization and heat treatment.\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/27bc2d46f28f2cdea1bb8df1.jpg"},{"id":80055329,"identity":"55ea0ff7-8c34-4a2d-a9c2-e9210a196de2","added_by":"auto","created_at":"2025-04-07 11:17:01","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":35892,"visible":true,"origin":"","legend":"\u003cp\u003eTop-view and cross-section SEM images of (a, d) DT, (b, e) OT\u003csub\u003e0.27\u003c/sub\u003e, and (c, f) OT\u003csub\u003e0.8 \u003c/sub\u003ecoatings.\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/a2f00ead606d9f5c06e2d216.jpg"},{"id":80055334,"identity":"656e4ca2-4c9c-49dd-aae9-30009dcef4bc","added_by":"auto","created_at":"2025-04-07 11:17:01","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":160982,"visible":true,"origin":"","legend":"\u003cp\u003eOptical micrographs and friction force curves of scratch tests of (a) DT, (b) OT\u003csub\u003e0.27\u003c/sub\u003e, and (c)OT\u003csub\u003e0.8\u003c/sub\u003e coatings.\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/2a2eaad78070e98cb28e3bef.jpg"},{"id":80055336,"identity":"b08aaa78-e1a5-4688-9930-28cd4f095442","added_by":"auto","created_at":"2025-04-07 11:17:01","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":163584,"visible":true,"origin":"","legend":"\u003cp\u003e(a) XRD patterns of DT, OT\u003csub\u003e0.8\u003c/sub\u003e, and OTC\u003csub\u003e0.8 \u003c/sub\u003ecoatings, (b) Raman spectrum of OTC\u003csub\u003e0.8 \u003c/sub\u003ecoatings\u003csub\u003e.\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/1e55ee352d9600d5a385831a.jpg"},{"id":80055332,"identity":"5989866d-e44f-40bb-8fdd-cc9e8b6c054e","added_by":"auto","created_at":"2025-04-07 11:17:01","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":18595,"visible":true,"origin":"","legend":"\u003cp\u003e3D AFM surface morphologies of (a) DT and (b) OT\u003csub\u003e0.8\u003c/sub\u003e coatings.\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/4a735aa566ef940f75ae7dd6.jpg"},{"id":80056143,"identity":"daca924a-a060-49ea-85b1-d57416f19b9e","added_by":"auto","created_at":"2025-04-07 11:25:01","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":18354,"visible":true,"origin":"","legend":"\u003cp\u003eSEM image of (a) the cross-sectional morphology of OTC\u003csub\u003e0.8\u003c/sub\u003e coating, and (b) the carbon layer on the surface of the insert.\u003c/p\u003e","description":"","filename":"Picture6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/d6fba58f76e37cce6f263c7e.jpg"},{"id":80056146,"identity":"7800d280-9072-4371-8f73-53ff6ac1a069","added_by":"auto","created_at":"2025-04-07 11:25:01","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":186821,"visible":true,"origin":"","legend":"\u003cp\u003eOptical micrographs and friction force curves of scratch tests of OTC\u003csub\u003e0.8\u003c/sub\u003e coating.\u003c/p\u003e","description":"","filename":"Picture7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/b26443c1f6fe947709a07a36.jpg"},{"id":80055337,"identity":"0b7934c5-06f1-40db-b92b-b22675f213a9","added_by":"auto","created_at":"2025-04-07 11:17:01","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":46146,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images and EDS analysis of the cross-section of (a) DTC and (b) OTC\u003csub\u003e0.8\u003c/sub\u003e coatings.\u003c/p\u003e","description":"","filename":"Picture8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/f2ce092305cd1298f81e78df.jpg"},{"id":80055342,"identity":"02e9fe1b-07cc-4776-a355-87834c23b512","added_by":"auto","created_at":"2025-04-07 11:17:01","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":339964,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Friction coefficient curves of OT\u003csub\u003e0.8\u003c/sub\u003e and OTC\u003csub\u003e0.8\u003c/sub\u003e coatings for the 900 s friction test. (b) Friction coefficient curve of OTC\u003csub\u003e0.8\u003c/sub\u003e coating for the long-term test. The 3D monography and the corresponding cross-sectional topography of (c) OT\u003csub\u003e0.8\u003c/sub\u003e and (d) OTC\u003csub\u003e0.8\u003c/sub\u003e coatings. (e) The wear rate of OT\u003csub\u003e0.8\u003c/sub\u003e and OTC\u003csub\u003e0.8 \u003c/sub\u003ecoatings.\u003c/p\u003e","description":"","filename":"Picture9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/f71f641fad1991e2f093c053.jpg"},{"id":80055345,"identity":"962aa50d-890f-4b1d-a9b2-0814c0f379f7","added_by":"auto","created_at":"2025-04-07 11:17:01","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":1292811,"visible":true,"origin":"","legend":"\u003cp\u003eThe optical images of (a) OTC\u003csub\u003e0.8\u003c/sub\u003e coating and wear track after sliding friction for (b) 1 h, (b) 2 h, and (d) 2.5 h, and (e) the corresponding Raman spectra.\u003c/p\u003e","description":"","filename":"Picture10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/12ccbbc41ec987aa4e066062.jpg"},{"id":80055346,"identity":"e7cc8ca9-f524-4f70-8888-0dce1692bc9a","added_by":"auto","created_at":"2025-04-07 11:17:01","extension":"jpg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":222298,"visible":true,"origin":"","legend":"\u003cp\u003eThe optical images of (a) DTC coating and (b) wear track after sliding friction for 1 h, and (c) the corresponding Raman spectra.\u003c/p\u003e","description":"","filename":"Picture11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/1e60fc0af980660b8f310f2c.jpg"},{"id":80055343,"identity":"7b59d2e3-a63c-41a9-9c76-9b6bd3731f96","added_by":"auto","created_at":"2025-04-07 11:17:01","extension":"jpg","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":72721,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic of the wear mechanism of (a) DTC and (b) OTC\u003csub\u003e0.8\u003c/sub\u003e coatings.\u003c/p\u003e","description":"","filename":"Picture12.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/49e3109be687d89b273de3d0.jpg"},{"id":81435476,"identity":"025f72c2-a9a6-4cae-8b41-932766d27727","added_by":"auto","created_at":"2025-04-26 11:23:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3216801,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/a0697d4a-0170-43d9-a15a-8707f66a0081.pdf"},{"id":80055341,"identity":"a2731b7a-0207-4301-8a46-9e70ad4620dd","added_by":"auto","created_at":"2025-04-07 11:17:01","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":204143,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementalMaterials.docx","url":"https://assets-eu.researchsquare.com/files/rs-6358874/v1/c657cd61e9a266b792d6387d.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Self-lubricating properties of carbon filled oblique angle deposition porous TiN coating","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eFriction and wear are the ubiquitous phenomenon that has diverse implications in many technological fields, which are often the core cause of the energy loss and parts damage [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Hence, there persists a relentless pursuit to reduce the coefficient of friction and diminish wear between mechanical components [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Solid lubricants, especially the carbon materials and transition metal disulfides, with their unique physical and chemical properties, have become an ideal solution to meet lubrication challenges in harsh environments and special working conditions, such as the high/low temperature environment, vacuum, and electrical condition [\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. However, solid lubricants face the problem of being easily removed by the friction force due to their easy shearing properties. Some efforts have been made to keep the solid lubricants on the friction interface. Among them, surface texturing technology has been widely regarded as the efficient way to improve the tribological performance of solid lubricants [\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Almost all relevant studies confirm that the surface texture serves as a reservoir to enhance lubricant retention and as a trap to capture wear debris [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. However, the rough surface rough surface of the surface texturing limits its application in precision equipment. Moreover, it is difficult to prepare a uniform texture on the hard materials, which usually have excellent wear resistance. For example, hard coatings prepared by physical vapor deposition (PVD) technology, including TiN, CrN, CrAlN, etc., are hard coatings with excellent wear resistance that are widely utilized in industry [\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePVD TiN coating is one of the most established engineering materials, which has a wide range of technical applications. It has long been employed as the protective coating in mold manufacturing, the automotive industry, aerospace, and other fields [\u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Interestingly, the PVD TiN coating tends to grow in columnar during the deposition, which provides a way to produce porous TiN coating [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Over the past 30 years, porous TiN coatings have been widely reported using the oblique angle deposition (OAD) technology, which is a special technique in PVD by inclining the substrate surface [\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. When deposited the TiN coatings by OAD, the obtained TiN coatings would acquire the structure of inclined nano-columns separated by intercolumnar porosity, due to the influence of the shadowing effect.[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] The inclination angle of the substrate affects shadowing effect, thereby influencing the porosity between the columns [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Due to the porous structure, OAD TiN coatings have been systematically applied in the fields such as sensor technology, electrochemistry, and catalysis [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. More interestingly, when it used as the friction pair, the pores in the OAD TiN can act as reservoir for storing and retaining solid lubricants.\u003c/p\u003e \u003cp\u003eHerein, porous TiN coating filled with lubricant carbon has been successfully prepared. The porous TiN coating was firstly prepared using OAD technology, and the effect of deposition gas pressure on the pore structure and mechanical properties of the coating was investigated. Then, carbon was embedded into the pores of TiN coating as solid lubricant through hydrothermal carbonization and heat treatment. The porous OAD TiN coating exhibits excellent storage and retention capabilities for lubricant carbon, and the lubricant carbon could be released from the pores to the sliding interface and reduce the friction as well as wear. The OAD TiN coating deposited at 0.8 Pa possessed a hardness of 20.36 GPa and a porosity of 13.7%, and it possesses the excellent tribological properties as carbon filling. It maintained a friction coefficient of below 0.4 for 8,100 s under a normal load of 2 N (the contact pressure of 0.89 GPa) and had a very low wear rate of 6.9\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e mm\u003csup\u003e3\u003c/sup\u003e/N\u0026sdot;m. Obviously, it provides a novel way for the design of high-performance lubricating coating.\u003c/p\u003e"},{"header":"2. Experimental method","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Preparation of coatings\u003c/h2\u003e \u003cp\u003eAll the coatings were deposited by using the arc ion plating technique. The stainless steel (SS 304) with the mirrored surface in rectangular size (20 mm\u0026times;20 mm\u0026times;5 mm) were applied as the substrate. The distance between Ti target and substrate is approx. 400 mm, and the depositions were carried out at 200 ℃. Before the deposition, the surface of substrate was further cleaned by Ar ion bombardment under the bias voltage of -1,200 V and Ar pressure of 1.0 Pa. Subsequently, to improve the surface activity and adhesion, a Ti sublayer was deposited at bias voltage of -200 V and sputtering Ar pressure of 0.5 Pa. Details of the preparation parameters of the TiN film are listed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Two porous OAD-TiN coatings were deposited at the sputtering N\u003csub\u003e2\u003c/sub\u003e pressure of 0.27 and 0.8 Pa with the inclination angle of 80\u0026deg;, which were designated as OT\u003csub\u003e0.27\u003c/sub\u003e and OT\u003csub\u003e0.8\u003c/sub\u003e coatings, respectively. As a contrast, a reference TiN coating with fully dense microstructure was also deposited at sputtering N\u003csub\u003e2\u003c/sub\u003e pressure of 0.8 Pa without inclination angle, namely as DT coating.\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\u003ePreparation parameter of the TiN film\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=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eItem\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDeposition temperature\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e200 ℃\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWorking pressure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.27 and 0.8 Pa\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eArc current\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e80 A\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eArc voltage\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17 V\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDeposition time\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30 min\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInclination angle\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003csup\u003e\u0026deg;\u003c/sup\u003e and 80\u003csup\u003e\u0026deg;\u003c/sup\u003e\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 as-prepared TiN coatings were placed into 1 M glucose solution and then sealed in a Teflon-lined stainless-steel autoclave to heat at 180 ℃ for 3 h. After the reaction treatment, samples were washed and dried at 60 ℃ for 12 h. Then, the samples were heat at 500 ℃ for 3 h at Ar atmosphere to get carbon filled coatings. The DT, OT\u003csub\u003e0.27\u003c/sub\u003e and OT\u003csub\u003e0.8\u003c/sub\u003e coatings were designated as DTC, OTC\u003csub\u003e0.27\u003c/sub\u003e and OTC\u003csub\u003e0.8\u003c/sub\u003e after the coatings were filled with carbon. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e depicts the schematic diagram of the preparation process of composite coatings.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Characterization of coatings\u003c/h2\u003e \u003cp\u003eThe surface and cross-sectional feature of the coatings were measured by using the scanning electron microscopy (SEM FEI Quanta FEG 250) equipped with EDS (Oxford, XMax). X-ray diffraction (XRD, D/MAX-RB, Rigaku, Japan) in grazing incident mode was used to characterize the crystalline structure of coatings at an incident angle of 1.5 \u0026deg;. Raman spectroscopy (DXR2, Thermo, USA) was performed on the surface after carbon filling. Nanoindenter (Step E400, Anton Paar, Austria) was used to perform the mechanical properties of TiN coatings. The adhesion of the coatings was determined by using automatic scratch teste (MFT-4000, Huahui, China). The applied load was increased from 0 to 50 N at a loading speed of 50 N/min. After the scratch test, the scratch tracks were observed by microscopes (Axio Image, ZEISS, Gemany).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Friction test\u003c/h2\u003e \u003cp\u003eFriction measurements were carried out on the planar surface of coating by using a ball-on-disk rotary tribometer. Measurements were made in ambient air at ~\u0026thinsp;32% relative humidity environments and room temperature. In the sliding process, a Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e ball of 8 mm in diameter was used as friction pairs, with a rotation speed of 200 rpm, rotation radius of 4 mm and normal load of 2 N. After friction test, the white light interferometry 3D profiler (MicroXAM-800, KLA-Tencor, USA) and Raman spectroscopy were carried out to analyze the wear tracks.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003e \u003c/p\u003e \u003cp\u003eThe structure of as-prepared TiN coatings was firstly investigated by SEM, as given in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Obviously, the DT coating shows dense and smooth surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea\u003cb\u003e)\u003c/b\u003e, and both the OT\u003csub\u003e0.27\u003c/sub\u003e and OT\u003csub\u003e0.8\u003c/sub\u003e coatings present crack-like pore structure(Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb, c). It should be noted that the pores in OT\u003csub\u003e0.8\u003c/sub\u003e coating is smaller and the structure is denser than OT\u003csub\u003e0.27\u003c/sub\u003e coating. The porosity of coatings was estimated by using an image processing program (Image J) from the SEM pictures.[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] The porosity of OT\u003csub\u003e0.27\u003c/sub\u003e and OT\u003csub\u003e0.8\u003c/sub\u003e coatings are about 7.5% and 13.7%, indicating that OT\u003csub\u003e0.8\u003c/sub\u003e coating may possess the more space to store solid lubricants.\u003c/p\u003e \u003cp\u003eFurthermore, the cross-section morphology of the coatings was also investigated. In Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed, the DT coating displays dense structure morphology. In comparison, the cross-section images reveal the obvious columnar structure for the OT\u003csub\u003e0.27\u003c/sub\u003e and OT\u003csub\u003e0.8\u003c/sub\u003e coatings. At the extreme inclination angle of over 80\u0026deg; for deposition, the shadowing effect dominates the mobility and diffusion of adatoms, result in forming porous and titled nanocolumns [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. The columnar structure of OT\u003csub\u003e0.27\u003c/sub\u003e coating (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee) is not clear, while the OT\u003csub\u003e0.8\u003c/sub\u003e coatings (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef) exhibits more uniform and smaller columnar structure. It can be ascribed to that more collisions generally occur at higher sputtering pressures, which limits the lateral mobility of atom, resulting in vertical columnar growth [\u003cspan additionalcitationids=\"CR34\" citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Thus, TiN column of OT\u003csub\u003e0.8\u003c/sub\u003e coating possess the obvious boundaries, with width of 160 nm and uniform height. As a result, the OT\u003csub\u003e0.8\u003c/sub\u003e coating shows uniform pores and flat surface. The average tilt angle of TiN columns in OT\u003csub\u003e0.8\u003c/sub\u003e coating remain at a low value of 12\u0026deg;. Apparently, porous TiN coatings prepared by cathodic arc evaporation could serve as the reservoir for lubricants.\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\u003eIndentation hardness (H) and elastic modulus (E) of deposited TiN coatings.\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=\"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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCoatings\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHIT (GPa)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eE (GPa)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e29.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e412.73\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOT\u003csub\u003e0.8\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e20.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e271.87\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOT\u003csub\u003e0.27\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e196.82\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 mechanical properties of all coatings were investigated by using the nanoindenter, and the results of hardness (H) and elastic modulus (E) are listed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The maximum penetration depth (\u003cem\u003eh\u003c/em\u003e\u003csub\u003emax\u003c/sub\u003e) is less than 0.1\u003cem\u003ed\u003c/em\u003e (\u003cem\u003ed\u003c/em\u003e\u0026thinsp;=\u0026thinsp;film thickness) [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. The H and E values of DT coating are 29.98 GPa and 412.73 GPa, which are much higher than OAD TiN coatings. This result indicates that tilted column and pore in coatings would decrease the mechanical performances, which may subsequently affect the tribological properties. Furthermore, the deposition pressure significantly affected the mechanical properties of OAD TiN coatings. The H and E values of OT\u003csub\u003e0.27\u003c/sub\u003e coating are only 12.64 GPa and 196.85 GPa, which are lower than those of OT\u003csub\u003e0.8\u003c/sub\u003e coating. It can be attributed to that the OT\u003csub\u003e0.8\u003c/sub\u003e coating has more uniform columnar structure, smaller tilt angle and pore size. The scratch test results demonstrate that adhesion of OT\u003csub\u003e0.8\u003c/sub\u003e coating is 34.1 N, a little bit higher than OT\u003csub\u003e0.27\u003c/sub\u003e coating. Due to tilted columnar and porous structure, the adhesion of both OAD TiN coatings are lower than dense DT coating (37.9 N). Thus, according to the abovementioned characterization results, OT\u003csub\u003e0.8\u003c/sub\u003e coating is selected as the candidate for subsequent study.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe crystalline structure of the DT, OT\u003csub\u003e0.8\u003c/sub\u003e, and carbon filled coatings (OTC\u003csub\u003e0.8\u003c/sub\u003e) were investigated by XRD and the patterns are given in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea. In low angle diffraction part, all the coatings show five peaks, corresponding to the (111), (200), (220), (311) and (222) plane of face-centered cubic (FCC) TiN [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. In comparison, the DT coating shows a (111) preferred orientation, while the OT coatings present a (220) preferred orientation. It can be ascribed to the fact that the vertical direction energy of the particles decreases as the substrate tilt angle increases, leading to a lower momentum of the particles bombarding the coating [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. As a result, the intrinsic stress of the OT coating should be lower than DT coating because the coating stress is determined by particle momentum [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. Thus, the OAD weakens the (111) orientation that always occur under high stress and displays (220) preferred orientation.[\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e] It should be noticed that the intensity of (200) peak increases in OTC\u003csub\u003e0.8\u003c/sub\u003e coating, which is attributed to heat treatment after hydrothermal carbonization. The (220) plane has the lowest surface energy in the FCC TiN crystal, which is contributed to improve the wear resistance and adhesion [\u003cspan additionalcitationids=\"CR42\" citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. The carbon species produced by hydrothermal carbonization treatment are usually amorphous, which cannot be detected by XRD measurement [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]. Therefore, Raman spectroscopy was used to characterize the coating. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb shows the Raman spectrum of OTC\u003csub\u003e0.8\u003c/sub\u003e coating. The spectrum shows typical carbon peaks at 1370 and 1596 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, corresponding to D and G peaks [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe roughness of DT and OT\u003csub\u003e0.8\u003c/sub\u003e coatings was investigated by AFM. As it shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, OT\u003csub\u003e0.8\u003c/sub\u003e coatings possesses the lower roughness (\u003cem\u003eRa\u003c/em\u003e of 194 nm) than DT coating (\u003cem\u003eRa\u003c/em\u003e of 251 nm). Nikhil et al. reported that the TiN with a predominant (200) orientation had a considerably smoother surface than the one with (111) orientation, which is consistent with the XRD results of OT\u003csub\u003e0.8\u003c/sub\u003e coating [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. The cross-sectional morphology of the OTC\u003csub\u003e0.8\u003c/sub\u003e coating was also investigated, and the SEM images are displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. It can be seen that the coating becomes dense and the columnar structure can still be observed (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea). However, the columns became more vertical after the hydrothermal treatment, which is beneficial for improvement of the adhesion of coatings. The scratch test reveals that the adhesion of OTC\u003csub\u003e0.8\u003c/sub\u003e coating on stainless steel substrate increases to 38.4 N (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). Furthermore, the carbon layer with thickness of 50 nm is covering on the OTC\u003csub\u003e0.8\u003c/sub\u003e coating surface, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb. To clarify that the carbon was successfully filled into the pores of the OTC\u003csub\u003e0.8\u003c/sub\u003e coating, EDS measurement was employed. As it shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, the signal of element C is sI intensive in the cross-section of OTC\u003csub\u003e0.8\u003c/sub\u003e coating, while it is weak for DTC coating. Thus, it can be demonstrated that the hydrothermal carbonization treatment can fill the carbon into the pores of OAD-TiN coating.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe tribological performance of OTC\u003csub\u003e0.8\u003c/sub\u003e coatings was investigated by using home-made ball-on-disc tribometer at normal load of 2 N and rotation speed of 200 rpm. For comparison, the tribological performance of OT\u003csub\u003e0.8\u003c/sub\u003e coating was also measured, and the frictional coefficient curves are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ea. It can be observed that the friction coefficient of OT\u003csub\u003e0.8\u003c/sub\u003e coating is very high and it can be worn out after sliding of 850 s. Notably, the OTC\u003csub\u003e0.8\u003c/sub\u003e coating maintains a low friction coefficient below 0.4 for ~\u0026thinsp;t 2.25 h (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eb). The tribological performance is also much better than that of DTC coating with initial COF of 0.3 for 1200 s and sequent COF over 0.85 (\u003cb\u003eFig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e\u003c/b\u003e). The initial low friction can be attributed to the lubricant carbon layer at the top of DT coating. However, this carbon layer can be easily removed by the friction behavior, leading to the increase in friction. Furthermore, the tribological performance of OTC\u003csub\u003e0.27\u003c/sub\u003e coating was also evaluated as shown in \u003cb\u003eFig. S2\u003c/b\u003e. In the initial 2,500 s sliding, the friction coefficient of OTC\u003csub\u003e0.27\u003c/sub\u003e coating is similar to the OTC\u003csub\u003e0.8\u003c/sub\u003e coating. Then, the friction coefficient of OTC\u003csub\u003e0.27\u003c/sub\u003e coating starts to increase and reaches up to 0.6 at 6,000 s. It is proved that the tribological performance of OTC\u003csub\u003e0.27\u003c/sub\u003e coating is inferior to the OTC\u003csub\u003e0.8\u003c/sub\u003e coating but much superior to DTC coating. The wear behavior of OT\u003csub\u003e0.8\u003c/sub\u003e and OTC\u003csub\u003e0.8\u003c/sub\u003e coatings after sliding friction of 900 s was evaluated. Figures\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ec,d present the 3D morphologies and corresponding cross-sectional topography of the wear tracks of OT\u003csub\u003e0.8\u003c/sub\u003e and OTC\u003csub\u003e0.8\u003c/sub\u003e coatings, respectively. The OT\u003csub\u003e0.8\u003c/sub\u003e coating has severe wear, with the depth of the wear track of 4.30 \u0026micro;m, which is higher than the thickness of OT\u003csub\u003e0.8\u003c/sub\u003e coating (~\u0026thinsp;2 \u0026micro;m), suggesting its worn out. As carbon component incorporated in the porous TiN coating, the OTC\u003csub\u003e0.8\u003c/sub\u003e coating possesses outstanding wear resistance with slight 0.22 \u0026micro;m depth wear track. The wear rate of OTC\u003csub\u003e0.8\u003c/sub\u003e is 6.9 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e mm\u003csup\u003e3\u003c/sup\u003e/N\u0026sdot;m, one of thirtieth of that of OT\u003csub\u003e0.8\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ee). It can be stated the combination strategy of fabrication of porous hard TiN coating and incorporation of lubricant carbon into the pores can significantly reduce the friction as well as wear behaviors.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo further elucidate the friction and wear mechanism, the optical microscopy and Raman spectroscopy measurement were conducted to analyze the sliding interface. Figures\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e and \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e display optical images and Raman spectra on the wear track of OTC\u003csub\u003e0.8\u003c/sub\u003e and DTC coatings after sliding friction different time, respectively. The initial surfaces of both as-prepared coatings are coated by the carbon layer (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ea and Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003ea), which show strong peak intensity of D and G bands (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ee and Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003ec). After sliding friction for 1 h, the optical image of OTC\u003csub\u003e0.8\u003c/sub\u003e coating shows a bright wear track covered with discontinuous dark carbon films that can play the dominant role in reducing the friction (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003eb). The friction behavior presents the high and fluctuant characteristics of COF of 0.35\u0026thinsp;~\u0026thinsp;0.40, due to the insufficient lubricant carbon film covering on the wear track surface. The weak D and G band Raman peaks in the bright region demonstrate the superior bearing capacity of porous TiN coating and reservoir and self-releasing features of lubricant carbon from the pores of the OT\u003csub\u003e0.8\u003c/sub\u003e coating. In contrast, for the DTC coating, the bright TiN has been fully exposed after sliding friction for 1 h, and the Raman spectrum shows no lubricant carbon presentation (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003eb). The wear track characteristics of the OTC\u003csub\u003e0.8\u003c/sub\u003e coating after testing for 2 h show a similar phenomenon to that of 1 h (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ec). These results demonstrate that the carbon stored in the OT\u003csub\u003e0.8\u003c/sub\u003e coating can be released to the sliding interface driven by the friction behaviors to reduce the friction as well as wear. Nevertheless, due to the pretty limited storage and supply amount of the lubricant carbon in the interior of the porous TiN based coating, the friction coefficient is relatively high but still much lower than pure TiN (such as DT and OT\u003csub\u003e0.8\u003c/sub\u003e coatings). Finally, after the carbon lubricant is completely released and consumed, the friction coefficient rapidly increases and the coating can be worn out, resulting in the fully exposure of the 304 substrate (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ed).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eOn the abovementioned, the friction and wear mechanism of the DTC and OTC\u003csub\u003e0.8\u003c/sub\u003e coatings can be illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e. Both surfaces of the DTC and OTC\u003csub\u003e0.8\u003c/sub\u003e coatings were covered by lubricant carbon layer after the hydrothermal carbonization treatment. In the initial sliding friction stage, the recombined lubricant film originating from the surface carbon layer on wear track driven by friction behaviors can reduce the friction as well as wear. Thus, both the DTC and OTC\u003csub\u003e0.8\u003c/sub\u003e coatings show a low friction coefficient of 0.2 at the initial 200 s sliding friction stage. As the sliding friction ongoing, the lubricant carbon film on the wear track of DTC coating is completely consumed, resulting in the full exposure of the TiN layer and increase in the friction (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003ea). Beneficial from the reservoir and self-releasing feature of lubricant carbon in the porous TiN coating, the recombined lubricant carbon film on the wear track surface driven by frictional behaviors can be maintained for long-terms. Thus, the robust friction reduction and high wear resistance was achieved. (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003eb). After this long steady friction stage, due to the limit amount of lubricant carbon in the reservoirs of the porous TiN coating, the formed carbon film become discontinuous, thereby, the friction coefficient slowly increases to 0.4. At this stage, the removal and formation of lubricant carbon film driven by friction behaviors achieve a balance. The lubricant performance failed as the interior carbon was fully released and consumed during friction process. Then, the OTC\u003csub\u003e0.8\u003c/sub\u003e coating evolved into the high friction level as the lubricant was absent.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eIn this study, the porous TiN coating was prepared by depositing the porous TiN coating via the oblique angle deposition technique, the lubricant carbon was then filled into the interior of the porous TiN by a combination of hydrothermal carbonization and heat treatment. The porous TiN coating acts as not only a load-bearing layer and the reservoir to store the carbon lubricant, which can release carbon to the sliding interface driven by friction behanviors, thus significantly reducing the friction and wear during sliding. Morphology and mechanical properties characterizations demonstrate that the porous TiN coating deposited at 0.8 Pa with an oblique angle of 80\u0026deg; possesses better mechanical properties, more uniform pores and higher porosity than the coating deposited at 0.27 Pa, suggesting the better capacities to bear the load and store the carbon. As a result, the friction coefficient of OTC\u003csub\u003e0.8\u003c/sub\u003e coating can be maintained below 0.4 for ~\u0026thinsp;8,100 s, longer than the ~\u0026thinsp;3,000 s of OTC\u003csub\u003e0.27\u003c/sub\u003e coating. Notably, both the OTC coatings are better than the DTC coatings, which reaches a high friction coefficient of 0.85 at ~\u0026thinsp;1,200 s. Moreover, OTC\u003csub\u003e0.8\u003c/sub\u003e coating also possesses a low wear rate of 6.9\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e mm\u003csup\u003e3\u003c/sup\u003e/N\u0026sdot;m. The excellent tribological performance of OTC coating demonstrates that the oblique angel deposition of hard porous coatings to store the lubricants offers a novel strategy to design the lubricating coatings.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eKai Le: investigation, visualization, data curation, funding acquisition, and writing of the original draft. Ke li: investigation , methodology, data curation. Yuzhen Liu: revision of the manuscript. Huijie Zhang and Lina Gao: data curation. Yong Luo: supervision and revision of the manuscript. Shusheng Xu: conceptualization, methodology, funding acquisition, supervision, and revision of the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThe authors are grateful for the financial support provided by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB0470102), the Natural Science Foundation of Shandong Province (No. 2022HWYQ-096), the Scientific Instrument Development Program of the Chinese Academy of Sciences (No. PTYQ2024YZ0006), the Key Instrument Development Program of the National Natural Science Foundation of China (No. 52427807), the Key Research Project of Shandong Provincial Natural Science Foundation (No. ZR2023ZD13), the Key Research and Development Program in Shandong Province (No. SYS202203), the Key Research Project of Shandong Provincial Natural Science Foundation (No. 2024KJHZ017), and the Program for Taishan Scholars of Shandong Province.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChen, H., Wang, W., Le, K., Liu, Y., Gao, X., Luo, Y., et al.: Effects of substrate roughness on the tribological properties of duplex plasma nitrided and MoS\u003csub\u003e2\u003c/sub\u003e coated Ti6Al4V alloy. Tribol Int. \u003cb\u003e191\u003c/b\u003e, 109123 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu, Y., Han, J.-H., Xu, S., Jung, Y.C., Kim, D.-E.: Dual in-situ observation of tribochemical and morphological evolution of single-layer WS\u003csub\u003e2\u003c/sub\u003e and multi-layer WS2/C coatings. Friction. \u003cb\u003e12\u003c/b\u003e, 1580\u0026ndash;1598 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu, R., Zhang, Y., Pu, J., Jie, M., Xiong, Q., Zhang, X., et al.: Wear Mechanism and Wear Debris Characterization of ULWPE in Multidirectional Motion. Tribol Lett. \u003cb\u003e72\u003c/b\u003e, 130 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDohda, K., Boher, C., Rezai-Aria, F.: Mahayotsanun, N. Tribology in metal forming at elevated temperatures. Friction. \u003cb\u003e3\u003c/b\u003e, 1\u0026ndash;27 (2015)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu, J., Yan, Z., Hao, J., Liu, W.: The influence of proton radiation on the friction and wear of Ti:WS\u003csub\u003e2\u003c/sub\u003e/P201 composite lubricating materials for space application. Wear. \u003cb\u003e538\u0026ndash;539\u003c/b\u003e, 15 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu, Y., Le, K., Han, J.-H., Teng, H., Xiu, Z., Jung, C.: Understanding the influence of carbon interlayers on material removal and tribochemical evolution in multilayer coatings through In-Situ analysis. Carbon. \u003cb\u003e230\u003c/b\u003e, 119593 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu, X., Le, K., Wang, J., Lin, H., Liu, Y., Jiang, F., et al.: Synergistic lubrication of multilayer Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e@MoS\u003csub\u003e2\u003c/sub\u003e composite coatings via hydrothermal synthesis. Appl. Surf. Sci. \u003cb\u003e668\u003c/b\u003e, 160400 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXu, S., Sun, J., Weng, L., Hua, Y., Liu, W., Neville, A., et al.: In-situ friction and wear responses of WS\u003csub\u003e2\u003c/sub\u003e films to space environment: Vacuum and atomic oxygen. Appl. Surf. Sci. \u003cb\u003e447\u003c/b\u003e, 368\u0026ndash;373 (2018)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRipoll, M.R., Simič, R., Brenner, J., Podgornik, B.: Friction and lifetime of laser surface\u0026ndash;textured and MoS\u003csub\u003e2\u003c/sub\u003e-Coated Ti6Al4V under dry reciprocating sliding. Tribol Lett. \u003cb\u003e51\u003c/b\u003e, 261\u0026ndash;271 (2013)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBao, Y., Deng, J., Wang, J., Wang, R., Sun, Q., Wu, J.: Tribological properties of Bi\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e3\u003c/sub\u003e/MoS\u003csub\u003e2\u003c/sub\u003e composite coatings deposited on biomimetic leaf vein textured surfaces. Tribol Lett. \u003cb\u003e71\u003c/b\u003e, 97 (2023)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNarayana, T., Saleem, S.S.: Enhancing fretting wear behavior of Ti64 alloy: The impact of surface textures and CrN-MoS\u003csub\u003e2\u003c/sub\u003e-Ag composite coating. Tribol Int. \u003cb\u003e193\u003c/b\u003e, 109346 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang, Z., Deng, J., Wang, R., Bao, Y., Dou, Z., Tang, X.: Wear Performance of Electro-Fluid Mask In Situ Forming TiO\u003csub\u003e2\u003c/sub\u003e-MoS\u003csub\u003e2\u003c/sub\u003e Alternate Coatings Under Different Friction Conditions. Tribol Lett. \u003cb\u003e72\u003c/b\u003e, 28 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFeng, X., Wang, R., Wei, G., Zheng, Y., Hu, H., Yang, L., et al.: Effect of a micro-textured surface with deposited MoS\u003csub\u003e2\u003c/sub\u003e-Ti film on long-term wear performance in vacuum. Surf. Coat. Technol. \u003cb\u003e445\u003c/b\u003e, 128722 (2022)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFu, X., Cao, L., Qi, C., Wan, Y., Xu, C.: Ultralow friction of PVD TiN coating in the presence of glycerol as a green lubricant. Ceram. Int. \u003cb\u003e46\u003c/b\u003e, 24302\u0026ndash;24311 (2020)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlkan, S., G\u0026ouml;k, M.S.: Influence of plasma nitriding pre-treatment on the corrosion and tribocorrosion behaviours of PVD CrN, TiN and AlTiN coated AISI 4140 steel in seawater. Lubr Sci. \u003cb\u003e34\u003c/b\u003e, 67\u0026ndash;83 (2022)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTiwari, S.K., Rao, A.U., Kharb, A.S., Avasthi, D.K., Verma, P.C., Chawla, A.K.: The effect of sputtering parameters and doping on the properties of CrN-based coatings\u0026mdash;A critical review. Surf. Interface Anal. \u003cb\u003e56\u003c/b\u003e, 479\u0026ndash;497 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePanjan, P., Drnovšek, A., Terek, P., Miletić, A., Čekada, M., Panjan, M.: Comparative study of tribological behavior of TiN hard coatings deposited by various PVD deposition techniques. Coatings. \u003cb\u003e12\u003c/b\u003e, 294 (2022)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChowdhury, M., Bose, B., Yamamoto, K., Shuster, L., Paiva, J., Fox-Rabinovich, G., et al.: Wear performance investigation of PVD coated and uncoated carbide tools during high-speed machining of TiAl6V4 aerospace alloy. Wear. \u003cb\u003e446\u003c/b\u003e, 203168 (2020)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlfath, S.A., Ponte, F., Sharma, P., Ferreira, F., Laranjeira, J., Carvalho, S., et al.: PVD decorative coatings on polycarbonate and polyamide substrates for the automotive industry. Surf. Interfaces. \u003cb\u003e52\u003c/b\u003e, 104887 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMareus, R., Mastail, C., Anğay, F., Bruneti\u0026egrave;re, N., Abadias, G.: Study of columnar growth, texture development and wettability of reactively sputter-deposited TiN, ZrN and HfN thin films at glancing angle incidence. Surf. Coat. Technol. \u003cb\u003e399\u003c/b\u003e, 126130 (2020)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJhajhria, D., Tiwari, P., Chandra, R.: Planar microsupercapacitors based on oblique angle deposited highly porous TiN thin films. ACS Appl. Mater. Interfaces. \u003cb\u003e14\u003c/b\u003e, 26162\u0026ndash;26170 (2022)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBouaouina, B., Mastail, C., Besnard, A., Mareus, R., Nita, F., Michel, A., et al.: Nanocolumnar TiN thin film growth by oblique angle sputter-deposition: Experiments vs. simulations. Mater. Des. \u003cb\u003e160\u003c/b\u003e, 338\u0026ndash;349 (2018)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNaas, L.-A., Bouaouina, B., Bensouici, F., Mokeddem, K., Abaidia, S.E.: Effect of TiN thin films deposited by oblique angle sputter deposition on sol-gel coated TiO\u003csub\u003e2\u003c/sub\u003e layers for photocatalytic applications. Thin Solid Films. \u003cb\u003e793\u003c/b\u003e, 140275 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMareus, R., Mastail, C., Nita, F., Michel, A., Abadias, G.: Effect of temperature on the growth of TiN thin films by oblique angle sputter-deposition: A three-dimensional atomistic computational study. Comp. Mater. Sci. \u003cb\u003e197\u003c/b\u003e, 110662 (2021)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHawkeye, M.M., Brett, M.J.: Glancing angle deposition: Fabrication, properties, and applications of micro-and nanostructured thin films. J. Vac Sci. Technol. A. \u003cb\u003e25\u003c/b\u003e, 1317\u0026ndash;1335 (2007)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSadeghi-Khosravieh, S., Robbie, K.: Morphology and crystal texture in tilted columnar micro-structured titanium thin film coatings. Thin Solid Films. \u003cb\u003e627\u003c/b\u003e, 69\u0026ndash;76 (2017)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMarques, S., Carvalho, I., Henriques, M., Polcar, T., Carvalho, S.: PVD-grown antibacterial Ag-TiN films on piezoelectric PVDF substrates for sensor applications. Surf. Coat. Technol. \u003cb\u003e281\u003c/b\u003e, 117\u0026ndash;124 (2015)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePedrosa, P., Machado, D., Fiedler, P., Vasconcelos, B., Alves, E., Barradas, N.P., et al.: Electrochemical characterization of nanostructured Ag: TiN thin films produced by glancing angle deposition on polyurethane substrates for bio-electrode applications. J. Electroanal. Chem. \u003cb\u003e768\u003c/b\u003e, 110\u0026ndash;120 (2016)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJen, Y.-J., Wang, W.-C., Wu, K.-L., Lin, M.-J.: Extinction properties of obliquely deposited TiN nanorod arrays. Coatings. \u003cb\u003e8\u003c/b\u003e, 465 (2018)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlMarzooqi, F.A., Bilad, M., Mansoor, B., Arafat, H.A.: A comparative study of image analysis and porometry techniques for characterization of porous membranes. J. Mater. Sci. \u003cb\u003e51\u003c/b\u003e, 2017\u0026ndash;2032 (2016)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRobbie, K., Sit, J., Brett, M.: Advanced techniques for glancing angle deposition. J. Vac Sci. Technol. B. \u003cb\u003e16\u003c/b\u003e, 1115\u0026ndash;1122 (1998)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBuzea, C., Kaminska, K., Beydaghyan, G., Brown, T., Elliott, C., Dean, C., et al.: Thickness and density evaluation for nanostructured thin films by glancing angle deposition. J. Vac Sci. Technol. B. \u003cb\u003e23\u003c/b\u003e, 2545\u0026ndash;2552 (2005)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMeese, W.J., Lu, T.-M.: Scaling behavior of columnar structure during physical vapor deposition. J. Appl. Phys. \u003cb\u003e123\u003c/b\u003e, 075302 (2018)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMazor, A., Srolovitz, D., Hagan, P., Bukiet, B.G.: Columnar growth in thin films. Phys. Rev. Lett. \u003cb\u003e60\u003c/b\u003e, 424 (1988)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDr\u0026uuml;sedau, T., L\u0026ouml;hmann, M., Klabunde, F., John, T.-M.: Investigations on energy fluxes in magnetron sputter-deposition: implications for texturing and nanoporosity of metals. Surf. Coat. Technol. \u003cb\u003e133\u003c/b\u003e, 126\u0026ndash;130 (2000)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJ\u0026ouml;nsson, B., Hogmark, S.: Hardness measurements of thin films. Thin solid films. \u003cb\u003e114\u003c/b\u003e, 257\u0026ndash;269 (1984)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang, J., Le, K., Chen, H., Zhao, X., Xie, X., Luo, Y., et al.: The significantly enhanced mechanical and tribological performances of the dual plasma nitrided and PVD coated Ti6Al4V alloy. Int. J. Precis Eng. Man. \u003cb\u003e24\u003c/b\u003e, 607\u0026ndash;619 (2023)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWindischmann, H.: Intrinsic stress and mechanical properties of hydrogenated silicon carbide produced by plasma-enhanced chemical vapor deposition. J. Vac Sci. Technol. A. \u003cb\u003e9\u003c/b\u003e, 2459\u0026ndash;2463 (1991)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChou, W.-J., Yu, G.-P., Huang, J.-H.: Mechanical properties of TiN thin film coatings on 304 stainless steel substrates. Surf. Coat. Technol. \u003cb\u003e149\u003c/b\u003e, 7\u0026ndash;13 (2002)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbadias, G., Tse, Y., Gu\u0026eacute;rin, P., Pelosin, V.: Interdependence between stress, preferred orientation, and surface morphology of nanocrystalline TiN thin films deposited by dual ion beam sputtering. J. Appl. Phys. \u003cb\u003e99\u003c/b\u003e, 113519 (2006)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOh, U., Je, J.H.: Effects of strain energy on the preferred orientation of TiN thin films. J. Appl. Phys. \u003cb\u003e74\u003c/b\u003e, 1692\u0026ndash;1696 (1993)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJones, M., McColl, I., Grant, D.: Effect of substrate preparation and deposition conditions on the preferred orientation of TiN coatings deposited by RF reactive sputtering. Surf. Coat. Technol. \u003cb\u003e132\u003c/b\u003e, 143\u0026ndash;151 (2000)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDiserens, M., Patscheider, J., Levy, F.: Improving the properties of titanium nitride by incorporation of silicon. Surf. Coat. Technol. \u003cb\u003e108\u003c/b\u003e, 241\u0026ndash;246 (1998)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYu, S., He, J., Zhang, Z., Sun, Z., Xie, M., Xu, Y., et al.: Towards negative emissions: Hydrothermal carbonization of biomass for sustainable carbon materials. Adv. Mater. \u003cb\u003e36\u003c/b\u003e, 2307412 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi, Y.-S., Jang, S., Khan, A.M., Martin, T.V., Ogrinc, A.L., Wang, Q.J., et al.: Possible origin of D-and G-band features in Raman spectra of tribofilms. Tribol Lett. \u003cb\u003e71\u003c/b\u003e, 57 (2023)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHashizume, N., Yamamoto, Y., Chen, C., Tokoroyama, T., Zhang, R., Diao, D., et al.: The Effect of Carbon Structure of DLC Coatings on Friction Characteristics of MoDTC-Derived Tribofilm by Using an In Situ Reflectance Spectroscopy. Tribol Lett. \u003cb\u003e72\u003c/b\u003e, 30 (2024)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePonon, N.K., Appleby, D.J., Arac, E., King, P., Ganti, S., Kwa, K.S., et al.: Effect of deposition conditions and post deposition anneal on reactively sputtered titanium nitride thin films. Thin Solid Films. \u003cb\u003e578\u003c/b\u003e, 31\u0026ndash;37 (2015)\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"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":"Oblique angle deposition, porous TiN coating, carbon, reservoir","lastPublishedDoi":"10.21203/rs.3.rs-6358874/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6358874/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTo address the issue of easy removal of lubricant phase by frictional behaviors, this study provided an innovative approach to fabricate porous TiN-based coatings subsequently filled by lubricants carbon. The process commenced with oblique angle deposition of porous TiN coatings, creating reservoir to store the carbon lubricants. The mechanical performance, pore size, and porosity can be adjusted through changing deposition gas pressure. The hardness increases from 12.64 to 20.36 GPa, and the pore size decreases, but the porosity increases from 7.5\u0026ndash;13.7% with rising working pressure from 0.27 to 0.8 Pa. Then, the carbon was filled into the pore of porous TiN through sequential hydrothermal carbonization and thermal treatment. The friction test results show that the carbon filled porous TiN coating deposited at 0.8 Pa possesses the excellent tribological performance, maintaining the friction coefficient below 0.4 for 8,100 s, which exceeds the ~\u0026thinsp;3,000 s of coating deposited at sputtering pressure of 0.27 Pa. There is no doubt that tribological performance of carbon filled porous TiN coatings are better than non-oblique angle deposited TiN-C coatings (\u0026micro;\u0026thinsp;\u0026asymp;\u0026thinsp;0.85 at 1,200 s). This coating also exhibits excellent wear resistance with a very low wear rate of 6.9 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e mm\u003csup\u003e3\u003c/sup\u003e/N\u0026sdot;m. The wear mechanism originated from continuous carbon release from pore TiN reservoirs to the wear interface, maintaining lubricating carbon films during sliding contact.\u003c/p\u003e","manuscriptTitle":"Self-lubricating properties of carbon filled oblique angle deposition porous TiN coating","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-07 11:16:56","doi":"10.21203/rs.3.rs-6358874/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":"3c26d319-fbba-4868-a2b4-75580a531502","owner":[],"postedDate":"April 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-04-26T11:23:22+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-07 11:16:56","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6358874","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6358874","identity":"rs-6358874","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}