Coatings properties Cr-Si-B-MgC2 in high conditions temperatures Language: Ukrainian

Abstract

Heat resistance, as well as friction and wear of composite coatings Cr–Si–B–MgC2 under conditions of elevated temperatures implemented in friction pairs, were investigated. The selection of the Cr–Si–B–MgC2 composition and its optimal composition for spraying wear-resistant coatings loaded with friction at high temperatures are substantiated. Indicated the main influence on the properties, structure, and stability of heterogeneous coatings is exerted by alloying elements at certain concentrations, as well as technological parameters of coating application. It has been established that silicon and boron contribute to the formation of complex-alloyed high-temperature formations with increased wear resistance. The microhardness of coatings correction is realized due to the silicon percentage content, while the mechanical properties of the material are increased by additional doping with boron and magnesium carbide. The parameters of sputtering of coatings are also important, on which the formation of a heat-resistant layer directly depends. It was experimentally established that the ratio of consumption of acetylene and oxygen ~20/25 l/min ensures the stability of technological parameters of sputtering, homogeneity of the chemical composition and constancy of coating properties. At a load of up to 5.0 MPa, a sliding speed of up to 1.2 m/s and a temperature of up to 700С, the coatings of the Cr–Si–B–MgC2 system show stable structural adaptability, which ensures the minimization of friction and wear parameters. Metallographic analysis and profilography of the samples indicate that there are no visible damages on the friction surfaces, and individual sticking points are localized in thin film surface layers. It was established that the dependence of the microhardness of the surface structures on the temperature is monotonic, but jumps are also observed if polymorphic transformations or transformations of metastable states into more stable and stable ones during heating and cooling occur. Microhardness indicators are uniform because particles of inclusions and impurities are dissolved in the oxide structures, which significantly affect the microhardness, and therefore, the properties of oxides of both simple and complex compositions. Keywords: protective coatings, surface layer, resistance to oxidation, wear resistance, heat resistance