Effect of chromium in substrate steel on the chemical vapour deposition of TiC

Abstract

TiC coatings on tools are widely used in order to increase their wear resistance. Chemical vapour deposition of TiC was performed on steels having different chromium contents in order to find a relationship between the chromium content in steel and the deposition characteristics of TiC. In the initial growth stage, the nucleation and growth was found to be strongly affected by the chromium content of the substrate steel. This result was attributed to the diffusion of carbon through the chromium-rich phase. Chromium element which increases the activation energy of carbon diffusion through the substrate steel reduces the deposition rate. A strongly preferred orientation of the (2 2 0) axis in the growth direction was found. Scanning electron micrographs showed that the grain was equiaxed for all experimental deposition conditions. They also showed that the grain size became finer with increasing chromium content in the substrate steels. Wear-resistance was improved with decreasing TiC grain size.