Thermodynamic analysis of reactions in the process of micro-arc steel chroming

It is shown that the existing chromizing processes are characterized by a number of shortcomings. It is proposed to use the microarc thermochemical treatment technology to form a carbide coating on the material surface. Thermodynamic calculations on the reducing reactions of chromium oxide which is the diffusion source are made. It is revealed that the most probable reaction behavior is the chromium oxide reduction by methane and carbon with the formation of atomic chrome, and a consistent formation of Cr 3C 2, Cr 7C 3, and Cr 23C 6 carbides with an increase in temperature. The obtained results are checked through experiments. As a result of the hardening processing, a surface layer on the basis of chromium carbides with the depth of 20-25 microns is produced under which there is a carbonized area of eutectoid concentration, followed by a baseline ferrite-pearlitic structure.