Abstract
Review of the main processes of formation of diffuse coatings doped with molybdenum,vanadium and tungsten. The basic features of the formation of diffusion layers during chemicalthermaltreatment are considered.: When the SHS is tested, the container is heated to temperaturesof 1173-1330 K. Within 1-2 hours, a diffusion coating is formed due to the saturation of thesurface of structural materials with atoms of saturating elements - Cr, Al, V, Ti, B, W, Mo. Assaturating elements, the defects of these elements and the chemical compounds of these elementswere used, and to determine the possibility of using specific substances, chemical reactionswere considered that can occur in the temperature range of diffusion saturation usingSOS. It should be noted that the metallothermal Reduced oxide, which is used in the synthesisof powder media for CHT, is very fast. When obtaining diffuse layers using the composition ofsaturating the medium, a gas phase is formed, containing spolo-I, I2, I3, H, H2, H3, Cl2, Cl3 withchemical elements. With an increase in temperature, an increase in the amount of halides isobserved. This confirms the possibility of transferring alloying elements for the formation of diffusioncoatings. Also, the amount of products in the gaseous phase increases and condensedproducts are released. It is characteristic that in the temperature range of 700-1500 K, the decompositionof reaction products occurs during CHT, which is confirmed by the production ofdecomposition substances and a sharp increase in the number of gas moles.
Highlights
Chemical heat treatment (CHT) of metals and alloys, consisting in saturation with various elements from the external environment in order to change the chemical and phase composition, structure and properties of the surface layers of the product, is a hightemperature process that has a complex multistage nature [1]
Classification of CHT processes according to saturation methods, the nature of the saturating element, etc. is given in the literature [2,3,4,5]
According to the modes of implementation, various methods of chemotherapy can be conditionally divided into two groups: a) traditional slow-flowing processes; b) intensive processes based on the use of fast heating, for example, highfrequency currents (HFC) or SHS processes, which, along with fast heat release and high temperature, are characterized by a short completion time of chemical reactions and phase transformations in a saturating mixture
Summary
Chemical heat treatment (CHT) of metals and alloys, consisting in saturation with various elements (metals or non-metals) from the external environment in order to change the chemical and phase composition, structure and properties of the surface layers of the product, is a hightemperature process that has a complex multistage nature [1]. When vanadium using a composite saturating medium, a gas phase is formed, which contains compounds H, H2, ОH, Cl, Cl2, Cl3, Cl6, 2Cl with chemical elements (Fig. 1). Gaseous products interacting with elements of the powder system (V, Сr) и go into the gas phase (appear AlH, AlH2, AlОH, AlCl2, AlCl3, Al2Cl6, AlHCl, AlH2Cl, AlОHCl2, CrO, CrH, CrOH, CrCl, CrCl2, CrCl3, CrOCl, CrОСl2,VО, VСl, VСl2, VCl3, VСl4).
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