MISE AU POINT D'UN TRAITEMENT DE CONVERSION DE SURFACE PAR DIFFUSION PRECIPITATION

Abstract

This present work concerns the development of an indirect method to produce chromium carbide coatings known for their properties of wear, corrosion and oxidation resistance and that by the combination of a treatment of metalloid diffusion and of an electrolytic coating of low carbon steels. This process of superficial hardening allows to increase and to improve the superficial properties of materials and more particularly those of the cutting tools. Treatment of conversion of surface by diffusion precipitation proposed is realized in three stages : The first stage is a pack carburizing or pack cementation (metalloid diffusion) by carbon on two low carbon steels : the XC18 and the 16MC5 (AFNOR NF A 35-551). The second stage concerns the deposition on the surface of treated steels a film of metallic chromium of a few μm (electrolytic coating). In the third step the parts previously obtained are heated at high temperature (annealing heat treatment) to convert the chromed surface into carbide by diffusion of carbon from the cemented zone towards chromed surface in order to obtain chromium carbide by precipitation. the characterizations of the elaborate coatings were carried by using the data from several physico-chemical and mechanical analysis techniques : the scanning electron microscopy (SEM), the X-ray diffraction (XRD) and the nanoindentation. The results obtained are relatively encouraging, however, complementary experiments are necessary and the development of this process needs to be improved.