Kapustian O. Increase of mechanical and service properties of welded joints of sintered structural titanium

The object of research is the process of structure formation in the weld, thermal and thermo-mechanical influence zones in products made of titanium powders. The subject of research is the patterns of the influence of structure on the mechanical properties and corrosion resistance of welded joints of titanium products obtained by powder metallurgy. The aim of the work is to increase the mechanical and service properties of welded joints of sintered titanium in products of complex configuration, obtained by complex technology and designed to work in corrosive environments. Research methods: improving the mechanical and service properties of welded joints of sintered titanium in products of complex configuration obtained by complex technology and designed to work in corrosive environments. Research methods: determination of the chemical composition was carried out by X-ray spectral and chemical methods, mechanical properties - by standard methods with static and shock loads, corrosion resistance - by the mass method. The study of the structure and fractures was performed by energy dispersive X-ray analysis and using optical and scanning electron microscopes, electrochemical tests using an IPC-Pro potentiostat in a potentiodynamic mode. For the first time, regularities were established for the formation of the structure of sintered titanium compounds obtained by pressure welding methods: contact butt fusion, convection friction and friction by mixing. For the first time, the influence of the structure of welded joints of titanium powder, obtained by friction welding by convection, on the resistance to corrosion processes in aqueous solutions of inorganic acids has been established. The idea of the influence of the fractional composition of the initial titanium powders on the formation of the structure, including porosity, as well as on the level of mechanical properties of sintered titanium was further developed. The understanding of the distribution of gaseous impurities of nitrogen and oxygen in the structural components of welded joints of sintered titanium during welding by contact butt fusion and convection friction in air is expanded. It was established that during welding at technological conditions gas saturation of the weld metal and the heat-affected zone is greater than the base metal. The results of the thesis were introduced in Public joint stock company "Titanium Institute" and at three industrial enterprises of Zaporozhye - LLC "Avia Sich", LLC "Zaporozhye Titanium & Magnesium Combine" and SE "Kremnypolymer".