SURFACE HARDENING OF CONSTRUCTION MATERIALS WITH THE USE OF COMPOSITE SATURATING CHARGES

Abstract

The article discusses the formation of the structure of protective diffusion layers using composite saturating charges on structural materials with different carbon content. A thermodynamic analysis of the gas phase at saturation has been carried out. The composition of the gas phase has been determined. Gaseous products interact with elements of the powder system (Al, Mo, Cr) and are transformed into the gas phase (CrH, CrOH, CrСl, CrСl2, CrСl3, СrОН, СrОСl2, CrI, CrI2, CrI3, МоСl, МоСl2, МоСl3, МоСl4, МоОСl, МоОСl2, МоI, МоI2, МоI3, МоI4). Using 3D modeling of microstructures, it was possible to more fully establish the nature of the distribution of phases and inclusions in the diffusion layer. The relationship between the 3D microstructure of the material and its physical and mechanical properties made it possible to carry out modeling to obtain the optimal composition of the developed composite charge for saturation. Diffuse layers are formed on the surface of structural materials, which contain Mo2C and α phases - the Cr, Al, Mo phase, the inclusion of Fе7Мо6, (Fe, Сr, Al, Mo)23С6. Carbides of three types were found: hexagonal chromium carbide Сr7C3 and carbides Мо2С, Cr23C, Fe3Mo3C и Fe2Mo2C. The physical, mechanical and operational properties of structural materials with protective diffusion coatings have been investigated. At tests in the conditions of sliding friction the best wear resistance among the considered diffusion coverings has vanadium, titanium and borized. Their wear resistance is 1.8 - 2.3 times greater than that of coatings obtained under isothermal conditions.