Method of reaction-sintered products processing based on silicon carbide and molibdenum disilicide

The study describes the properties of the protective coating deposited on the surface of the reaction-sintered silicon carbide and molybdenum disilicide. The technology of increasing the protective ability of the coating of products deposited on the surface on the basis of reactive sintered carbide of silicon and molybdenum disilicide, which operate in an oxidizing environment at high temperature and a sharp change of thermal regime, is investigated. The obtained results showed that the presence of a protective slip layer significantly increases the stability of the deposited silicoboride coating, thus blocking the interaction of silicon hexaboride with the environment, slowing down almost all diffusion processes at the transition of the interaction of diffusion. It has been established that the simultaneous use of both diffusion and slurry coatings enables maximum protection of reaction-sintered ceramic materials based on silicon carbide and molybdenum disilicide against high-temperature gas corrosion. The developed coating ensures maximum resistance to repeated changes in temperature conditions, while cyclic changes destroy products of silicon carbide and molybdenum disilicide without applied protective coating. The proposed protective coating can be recommended for the protection of reaction-sintered ceramic materials operated in high temperatures.

Research of properties of protective coating applied to the surface of reaction-sintered ceramic materials

Kovbashyn¹,

Bochar²

2021

The study of technological peculiarities for improvement of chemical and physico-mechanical properties of reaction-sintered ceramic materials based on molybdenum disilicide

Kovbashyn¹,

Bochar²

2022

Recommended ways to improve the chemical and physico-mechanical properties of reaction-sintered ceramic materials based on molybdenum disilicide have been described. In order to significantly increase the operating temperatures and change to more stringent operating conditions for ceramic products, it is necessary to improve existing methods of processing ceramics and significantly change the development of new ones. Various means for processing of ceramic materials have been studied and analyzed, which include the introduction of activating additives, hardening with dispersed particles, filamentary crystals and fibers and application of a protective coating to prevent rapid oxidation at surface layers. Carrying out partial purification of the initial starting components from various impurities can significantly increase some characteristics of the disilicide of molybdenum ceramics. Disilicide of molybdenum ceramics has been researched to have significant influence on the physical and mechanical properties (thermal conductivity, electrical resistance, coefficient of thermal expansion and strength) of molybdenum ceramics disilicides, which are introduced into the base material both with the initial components and in the process of its technological production. It has been established that it is possible to increase operating temperatures and ensure the use of molybdenum disilicide-based ceramic materials in harsher working conditions can be achieved by introducing of aluminum, boron, beryllium, iron, yttrium, nickel and cobalt powders into the charge, strengthening titanium coating, which includes silicification and titanium technology. It has been researched that at high temperatures and in the presence of molten silicon the synthesis and crystallization of molybdenum dicilicide occur on the grains in the surface layers, as well as dissolution and recrystallization of submicron particles of molybdenum dicilicide take place at certain depth. Based on the published data analysis and conducted research, the complex of measures for improving the chemical and physico-mechanical properties of reaction-sintered ceramic materials based on molybdenum disilicide has been proposed.

Investigation of the change in technological properties of refractory metals after diffusion saturation

Kovbashyn¹,

Bochar²

2023

The recommended ways of improving the technological and physico-mechanical properties of refractory metals (molybdenum and tungsten) after diffusion saturation with the elements of the same name are described. In order to increase significantly the performance characteristics and transition to stricter operating conditions for products made of refractory metals, it is necessary to improve the existing methods of processing metals and make significant changes in the development of new ones. Different directions of refractory metals processing, which involve diffusion saturation with elements of the same name, introduction of activating additives into the composition of the diffusion mixture, use of isothermal conditions during chemical-thermal treatment, and application of protective coating to improve technological and physical-mechanical properties, have been studied and analyzed. To evaluate changes in the mechanical properties of molybdenum and tungsten after diffusion saturation with the elements of the same name, appropriate tests were conducted. To study the changes in the technological and physical and mechanical properties of refractory metals after the process of diffusion saturation in active-aggressive environment, tests on static rupture and stretching, bending, impact bending and buckling were carried out. It has been established that it is possible to increase the technological characteristics and ensure the use of refractory metals in harsher operating conditions by introducing molybdenum and tungsten powders of the same name and activating additive (sodium fluoride) into the charge to obtain protective coating. Comparison of the magnitude of the temporary resistances values for of untreated samples breaks of refractory metals and samples that have undergone the appropriate heat treatment showed significant decrease in these indicators after diffusion saturation with the same elements (molybdenation and tungstenization). Based on the analysis of literature data and conducted research, a set of measures aimed at the improvement of technological and physico-mechanical properties of refractory metals (molybdenum and tungsten) after diffusion saturation with the same elements in powder medium is proposed.