Improving the mechanical properties of 17-4PH stainless steel by low temperature plasma surface treatment

17-4PH stainless steel was plasma nitrocarburized at low temperature for improving its mechanical properties. The results show that the modified layer thicknesses increase with increasing treatment time and the layers growth approximately conforms to the parabolic law. The phases in the modified layers are mainly of incipient γ′-Fe₄N and α′-Fe with amorphous characterization, and then changed into γ′-Fe₄N, α′_N and traces of CrN with the treatment time increasing. The hardness of the nitrocarburized specimen is more than 1280 HV, which is about 3.5 times as hard as the untreated one. Meanwhile, the wear resistance of the steel specimen can be dramatically improved by plasma nitrocarburizing. The surface hardness and the wear resistance of the nitrocarburized specimens slightly decrease with an increase in treatment time for the surface hardness as well as microstructure changing.