Study of the Influence of V, Mo and Co Additives on the Carbide Formation and Microhardness during Thermal Diffusion Chrome Planting of X35CrNi2-3 Steel

Abstract

Saturation diffusion with chromium has not been adequately studied among all the surface thermochemical treatment (STCT) processes of steels. Especially, the complex saturation behavior when several elements are added directly for chemical treatment needs to be systematically studied. This work aims at determining the effect of V, Mo, and Co on the parameters of chromium thermal saturation diffusion (thickness, phase composition, microstructure, and microhardness) of the surface layer in X35CrNi2-3 steel. The process was carried out at a temperature of 1000 °C for 24 h. The results showed that complex structural chromium plating together with the addition of strong carbide-forming elements (V and Mo) has a significant effect on the phase composition of the fabricated layer, where the formation of VC and Mo2C carbides significantly increases the microhardness of the samples to 2000 HV and 2500 HV, respectively. On the other hand, the addition of Co with a less carbide-forming affinity has little effect on the phase composition of the coating, and nitride compounds predominated in the microstructure similar to the single-element chromium plating. The results indicate the possibility of improving and accelerating the traditional thermal chromium plating processes and opening up new horizons for obtaining gradient coatings with superior tribological properties.