Titanium-modified plasma nitriding layer and enhanced properties for 42CrMo steel

Abstract

In order to obtain a nitriding layer with thicker ductile diffusion layer and thinner brittle compound layer, plasma nitriding with titanium addition was carried out at 540 °C for 4 h for 42CrMo steel, the characteristic of titanium modified nitriding layer and the enhanced properties were systematically investigated by optical microscope (OM), scanning electron microscope (SEM), XRD, hardness tester and wear tester etc. The results show that titanium addition can effectively modify the characteristics of nitrided layer, and thus a plasma nitrided layer owning thicker ductile diffusion layer and thinner brittle compound layer and higher surface hardness can be obtained. Titanium addition can significantly decrease the compound layer and increase the effective hardening layer, and also greatly enhance the surface hardness, especially with the optimal amount of 0.8 g, the compound layer can be reduced from 19 μm to 10 μm, while the effective hardening layer can be increased from 225 μm to 370 μm. And the surface hardness can be enhanced from 703HV0.05 to 889HV0.05, more importantly, both wear resistance and toughness can be greatly promoted by the novel titanium modified plasma nitrided layer, attributed to the formation of dispersedly distributed TiN particles with very high hardness in the nitriding layer.