Microstructural and mechanical properties of chromium carbide thin layers elaborated by conversion treatment process with two methods on 16Mn2 steel

Abstract

The present study has been conducted in order to obtaining chromium carbide layers on 16Mn2 steel using a conversion processing comprising the following steps: carburizing in solid medium in order to increase the amount of carbon atoms in the steel surface, deposition of a thin layer of pure chromium using electrolytic method, and finally an annealing treatment for carbon diffusion and formation of chromium carbide layer until complete transformation of chromium layer. Depending on the method used (chromium deposition followed by carburizing or carburizing followed by chromium deposition) and the holding time, the partial or complete conversion is obtained as a result of the diffusion process. The role of the annealing temperature on transformation rates of chromium into chromium carbide films was investigated. It is shown that for 1 h at 900°C, the chromium layer is totally transformed. The scanning electron microscopy analysis and X-ray diffraction showed the presence of Cr3C2, Cr7C3 and Cr23C6 chromium carbides in addition of (Cr, Fe)7 C3, Fe2O3 and Cr2O3.