The Influence of Carburizing‐Nitriding Composite Heat Treatment on the Friction and Wear Properties of 20Cr3MoWVA Steel

Herein, the 20Cr3MoWVA steel is subjected to carburizing and plasma nitriding composite heat treatment for strengthening. Ball‐disk friction wear tests are conducted on three states (Untreated, C, C + PN) of the samples. The results show that after the composite heat treatment, a composite diffusion layer composed of γ′‐Fe 4 N phase and ε‐Fe 2‐3 N phase is obtained. This diffusion layer has no compound layer and no vein‐like grain boundaries, and its thickness is 150 micrometers. The surface hardness of the C + PN sample (1004 HV) is 4.2 times and 1.3 times that of the Untreated sample and the C sample, respectively, and its wear rate decreases by 97.34% and 74.38% compared to the untreated sample and the C sample, respectively. The C + PN sample has the lowest friction coefficient (0.5887), and the surface residual compressive stress reaches −883 MPa. During the plasma nitriding process, Cr‐rich M 7 C 3 carbides and V‐rich MC carbides transform into M 2‐3 (C, N) and M(C, N) carbonitrides, respectively. The wear mechanisms of the three specimen states involve oxidative wear and adhesive wear, with abrasive wear also present in the untreated and C specimens. During the wear process of the C + PN samples, nanocomposite self‐lubricating oxides with excellent wear resistance are formed.