Study of the chemical process of surface layer formation during plasma heating of a coating containing an alloy of the NiCrBSi system

The analysis of the possibility of the chemical process of forming a surface alloyed layer is carried out. The results of preliminary experiments on the formation of surface layer phases using an alloy of NiCrBSi systems are presented. According to theoretical studies, there are possible crystal structures, but almost all of them are not formed. The benefits of forming phase crystal structures depend on the Gibbs free energy. During the remelting process, the coating and several substrates melt. Under the convection of plasma arc remelting, the nickel-based alloy powder entered the molten pool. It is shown that with increasing temperature the Gibbs free energy decreases. This indicates that the synthesis reaction has a higher probability of occurring at high temperature. Ni2Si was found to have lower free energy than Cr3Si, but this does not mean that Ni2Si is the most likely phase to form in coatings. Cr3Si has a higher melting point (2043 K) than Ni2Si (<1728 K), therefore, the Cr3Si phase began to crystallize and precipitate before the for-mation of Ni2Si. Ni was enriched in interdendritic Cr3Si. At high temperatures, Cr6Ni16Si7 and Cr3Ni5Si2 had lower free energy than Ni2Si and Cr2Ni3, respectively. Comparing the Gibbs free energy, he comes to the conclusion that the prob-ability of formation of a number of phases Cr3Si, Ni2Si, Cr2Ni3, Cr6Ni16Si7, Cr3Ni5Si2 is significantly less for a number of Cr23C6, Cr7C3, CrB, Ni3B. It has been confirmed that to form a surface alloy layer, a complex process of action occurs between several components contained in the alloy and adhesives. A study of the thermodynamics of possible reac-tions noted that the probability of the formation of γ-Cr, γ-Ni, γ-Fe, (Fe, Cr)23C6, Cr23C6, Cr7C3, CrB, Ni3B, Ni3Si phases is significantly higher than that of other phases, as well as Cr3Si, Ni2Si, Cr2Ni3, Cr6Ni16Si7, Cr3Ni5Si2. The remaining products from plasma heating are possibly metal oxides, which can be released on the surface of the coating as welding slag.