Effect of ultrasonic nanocrystal treatment combined with nitriding process on fretting wear behavior of textured 20CrMoH steel

Individual and synergy effects of laser surface texturing (LST) followed by plasma nitriding (PN) and surface ultrasonic nanocrystal technology (SUNT) on fretting wear behaviors of 20CrMoH steel were systematically investigated at various loads and lubrication conditions. Results indicated that the combined treated (LST + PN + SUNT) 20CrMoH steel got the lowest surface roughness Ra value of 0.46 μm, the highest surface microhardness of 940 HV0.2, and the maximum residual compressive stress (RCS) value of −750 MPa. Consequently, the best fretting wear resistance was obtained by the combined treated 20CrMoH steel. Wear loss of untreated specimen reduced by 131 % after the combined treatment. The predominant wear mechanisms of the untreated, PN treated and LST + PN treated 20CrMoH steel under dry friction were oxidation wear and delamination. Besides, Oxidation and adhesion occurred for the combined treated specimen in dry friction. Especially, texture, residual stress and microhardness are key factors enhancing the anti-wear resistance.