Chornoivanenko K. Formation of the composite structure in surface layer with heightened physical and mechanical properties in high-alloyed iron alloys under complex chemical-thermal treatment

The dissertation is directed to definition of principles of structural and phase transformations under complex chemical-thermal treatment in high-alloyed iron alloys and development the technology of production of cast metal-cutting tool with the structure of natural composite in surface layer with heightened technological, working and mechanical characteristics. The rational operating regimes of complex chemical-thermal treatment of cast high-alloyed iron alloys, including a preliminary decarburization and subsequent carbonization of the surface layer, which provides the formation of natural composite structure in the surface layer of tool with improved performance characteristics have been investigated. The peritectoid transformations in high-alloyed iron alloys, which occurs in isothermal conditions under decarburization were firstly discovered, and a mathematical model of this transformation. The degree of deformation of the carbon-free high-alloyed iron alloys, which gives the maximum thickness and dispersion of the composite structure of the surface layer of tool after the subsequent carbonization has been installed. The influence of lattice defects on the diffusion mobility of interstitial and substitutional atoms by the final heat treatment in high-iron alloys after complex chemical and thermal treatment was defined. The technological process of producing materials with the structure of natural composite in surface layer was developed. PJSC "Dnepropetrovsk's aggregate plant" showed intention to establish the area of chemical-thermal treatment for this technology. The results of this work are using in the educational process in National Metallurgical Academy of Ukraine.