Effect of laminar plasma jet surface hardening on the abrasive wear and erosion behavior of 42CrMo steel

To encounter the challenging service conditions in mining and oil and gas exploration, Laminar plasma jet (LPJ) surface hardening was applied to enhance the abrasive wear and erosion resistance of 42CrMo steel. Tribological performance was evaluated using ball-on-disc tests with SiO₂ particles at the friction interface, while erosion resistance was tested under slurry immersion conditions. Surface morphological features and elemental composition were analyzed through scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to investigate the associated wear and erosion mechanisms. LPJ surface hardening produces a hardened layer composed of lath martensite, increasing the surface hardness to 1.89 times that of the untreated steel. As a result, the wear rate is reduced to 0.79 times that of the untreated sample, due to a shift in the wear mechanism in the ball-plane direct contact zone from an aggressive ploughing mechanism characteristic in two-body abrasive wear to a mild adhesive wear-dominated mechanism, potentially accompanied by localized oxidative wear. Additionally, erosion resistance is significantly improved due to the martensitic transformation of the surface microstructure, which offers higher yield strength and deformation resistance. This transformation alters the erosion mechanism from intense ductile erosion, which is characterized by extrusion and forging mechanism and ploughing mechanism, to a relatively mild brittle erosion, dominated by deformation mechanism and microcutting mode Ⅰ.