Yaskiv O. Development of fundamentals of technologies of carbonitride and carbooxide diffusion coatings formation on titanium alloys

Commercial titanium alloys of various grades with diffusion carbonitride and carbooxide layers were considered. The purpose was to develop the physical and chemical fundamentals of forming of ternary compounds (titanium carbonitrides and carbooxides) during thermodiffusion processing of titanium alloys in carbon-nitrogen-oxygen-containing media and to substantiate the technological approaches to formation of carbonitride and carbooxide coatings of regulated composition and morphology with increased level of wear- and corrosion resistance . Experimental examination included: optical and SEM analysis; microhardness measurement, roughness measurement; X-ray and EPMA analysis, tribological tests; mechanical tests corrosion examinations. The ranges of gas-dynamic parameters for the formation of ternary compounds at thermodiffusion processing have been found. It was shown that during noncontact carbonitriding and carbooxidizing of titanium alloys at 800...850оС an interaction of titanium with carbon takes place through gaseous carbon monoxide. It was proved that formation of carbooxide and carbonitride compounds takes place through formation of binary compounds (nitrides and carbides) of nonstoichiometrical composition and their further transformation in ternary compounds due to the interaction with active components (carbon, nitrogen, oxygen) of medium. It was shown that wear resistance of ternary compounds is higher than those for binary compounds. It was revealed that coatings based on ternary compounds of equiatomic composition reveal the best anticorrosion properties and in concentrated aqueous solutions of inorganic acids such coatings provide better resistance as compared to binary compounds. Carbonitride and carbooxide coatings formed on VT6, T110 and VT22 alloys were tested on airspace bureau "Antonov". The results of investigation have been using during chemical-heat treatment of parts of undercarriage of planes AN.