Improvement of the adhesive wear resistance of steel by nitriding quantified by the energy dissipated in friction

Chromium molybdenum types of steel are widely used in industry. The performance of 42CrMo4 steel parts can be improved by various types of processing of the bulk or surface. In the present study, we apply a thermochemical nitriding treatment to 42CrMo4 steel of returned martensite structure. This hardening treatment confers to this steel a multi-layer aspect including a compound layer, a diffusion layer and the base metal. The study relates to the performance of these layers with respect to adhesive wear. The parameters employed to evaluate the wear resistance of each layer are the contact pressure and the kinematics length. Three-dimensional wear maps (K, P, L) were produced and the results were analyzed in terms of the volume lost during wear as a function of the energy dissipated, for nitrided steel with and without the compound layer, and for untreated steel. The results prove that the nitriding treatment appreciably improves the adhesive wear resistance. Furthermore, this study contains an analysis of the wear mechanisms of a nitrided part, founded on scanning electron microscopy (SEM) observations of the wear traces and debris collected at various stages of the evolution of wear. This analysis shows that the principal wear mechanism is determined by the energy level deployed.