Comparison of the Activation Energies of the Formation of Chromium Carbide Coating on Carburized and Uncarburized AISI 1020 Steel

Abstract

Chromium carbide coatings deposited by the salt bath method have a lot of technologically interesting characteristics. This method produces hard, wear–resistant, oxidation and corrosion–resistant coating layers on steel substrates. In the present study, the kinetics of chromium carbide formation on carburized and uncarburized AISI 1020 steel substrates has been compared. The presence of the Cr7C3 phase on the surface of steel substrates was confirmed by X-ray diffraction. Cross–sectional observation of optical and SEM images showed that chromium carbide layers formed on the steel substrates were rather compact and smooth. The kinetics of chromium carbide coating by salt bath immersion indicated a parabolic relationship between carbide layer thickness and treatment time. The activation energy of the formation of carbide on the surface of carburized and uncarburized steel was calculated to be 87.9 and 225.6 kJ/mol, respectively. Moreover, an attempt was made to present contour diagrams for predicting the thickness of the chromium carbide layer. In addition, the possibility of establishing and using some mathematical relationships between process parameters and chromium carbide layer thickness was investigated.