Influence of Nitrogen Content in the Working Gas Mixture on the Structure and Properties of the Nitrided Surface of Die Steel

The paper presents the results of studies of the phase composition and structure of the nitrided layer of Cr6VW die steel formed by ion-plasma nitriding in a plasma of a non-self-sustained low-pressure glow discharge with a hollow cathode, as well as an analysis of the physicomechanical properties of the material surface. It was found that the nitrogen content in the plasma-forming gas mixture significantly affects the phase composition of the surface of the nitrided layer. After nitriding, the microhardness of steel in a layer up to 50 µm thick increases to ~ 11 GPa. The smallest surface wear was obtained as a result of nitriding of Cr6VW steel with a nitrogen content of 10% in a nitrogen-argon gas mixture at a working pressure of 1 Pa. The regularities revealed during the studies make it possible to control the structure and phase composition of the nitrided layer by changing of the ratio of N2 and Ar content in the nitrogen-argon mixture at low pressure and the magnitude of the negative bias voltage applied to the substrate.