A study on kinetics of CrxC-coated high-chromium steel by thermo-reactive diffusion technique

There are a lot of technologically interesting characteristics of chromium carbide coating deposited by pack method which is the production of hard, wear-resistant, oxidation- and corrosion-resistant coating layer on the steel substrates. In the present study, kinetic study of chromium carbide coating of AISI D2 steel coated by pack method at the temperature of 1223, 1273 and 1323 K for 1-4 h was realized. The presence of phases Cr7C3 and Cr3C2 formed on the surface of steel substrates were confirmed by X-ray diffraction analysis. Cross-sectional observation of optical and SEM back-scattered electron images (SEM-BEI) showed that chromium carbide layer formed on the steel substrates were smooth and compact. The hardness of chromium carbide layer is 1850±35 HV0.025. The kinetics of chromium carbide coating by pack method showed that a parabolic relationship between carbide layer thickness and treatment time, and activation energy for the process is 278 kJ/mol. Moreover, an attempt was made to investigate the possibility of predicting the contour diagram of chromium carbide layer variation and to establish some empirical relationships between process parameters and chromium carbide layer thickness.