Ceramic cutting materials are modern, promising tool materials due to their high hardness and resistance to wear, heat, diffusion, and oxidation. An important advantage of ceramic cutting materials is their relatively low cost and the absence of expensive and scarce components in their composition. Meanwhile, an increased tendency toward brittle fracture significantly limits the scope of application of tools made of cutting ceramics. Wear-resistant coatings of various compositions were used not only to increase the surface hardness and wear resistance but also to improve the crack resistance and tendency toward brittle fracture (in particular, due to the “healing” effect and the transformation of contact stresses in the cutting zone). Several studies have dealt with the deposition and use of diamondlike carbon (DLC) coatings on ceramic substrates, whereas virtually no studies have considered ceramic cutting tools with DLC coatings. In Ref., issues concerning increasing the operational properties of ceramic tribological pairs (particularly, slider bearings) were considered. In addition, SiC was used as a substrate, and a radical decrease in the coefficient of friction (COF) during the deposition of a DLC coating was observed. Later, noted excellent chemical stability, a low COF, and excellent wear resistance of ceramic products made of SiC with a DLC coating. Several researchers have considered the properties of a DLC coating deposited on an Si3N4 substrate. Gomes et al. considered DLC and DLC-Si coatings deposited on the above substrate. The tribological properties of uncoated samples and samples with the above coatings were studied under friction with a sample of stainless steel. Both coatings exhibited good tribological properties, but delamination from the substrate was observed for samples with DLC-Si coatings, and the wear coefficient for samples with DLC coatings was much lower than for samples with DLC-Si coatings. Similar results have been presented by Ref., who studied the properties of ceramic (Si3N4) mechanical face seals with DLC and DLC-Si coatings. The use of DLC and DLC-Si coatings significantly reduced the COF and increased the wear resistance of products. Meanwhile, DLC coatings demonstrated a better result compared to DLC-Si coatings. Several studies have noted that the introduction of Si into the composition of DLC coatings can significantly improve heat resistance and expand the application scope. A DLC coating deposited on a substrate of Si3N4 and M50 steel was considered. The normal stresses at the coating-substrate interface were higher (by about 10%) for the ceramic substrate, which could be explained by the higher elastic modulus of Si3N4. Meanwhile, transverse stresses were minimal with a minimum difference in the elastic modulus between the coating and substrate. In addition, as the coating thickness increased (from 200 to 400 nm), the stresses on the coating-substrate interface decreased, which occurred under the law of quadratic expression and slowed as the coating thickness increased. In Ref. the properties of the DLC coating deposited on substrates of Si3N4 were also considered. The results of the ball-on-disk wear tests showed both the wear of the coating and its delamination from the substrate. Moreover, in Refs., a sample with a DLC coating was characterized by a lower COF compared to a sample with an MoS2 coating. Furthermore, during the deposition of the above coatings, the roughness of the ceramic surface reduced significantly.
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