To enhance the frictional wear performance of AZ31B magnesium alloy, a nanocrystalline layer was prepared by ultrasonic impact (UI) treatment on magnesium alloy samples, and the effects of different ultrasonic impact times (5 min, 10 min, and 15 min) on the organization and wear resistance of the composite coating were studied. The findings revealed that the maximum thickness of the composite coating was about 50 μm after 10 min of impact time, which was approximately 15 μm higher than that of the MAO coating. The elemental composition of the composite coating was mainly Mg, O, and Si elements, and the phase structure of the coating, mainly MgO and Mg₂SiO₄, was the same before and after UI. The microhardness value gradually decreased in a gradient with the increasing distance from the sample surface. The coating had a lower average coefficient of friction (0.18) and lower wear loss (1.56 mg) for the 15 min impact time. Moreover, a small amount of abrasive and adhesive wear served as the primary modes of wear.

To investigate the effect of recovery treatment on the microstructure and tribological properties of ultrasonic impact-treated Al₂FeCoNiCrW_0.5 high-entropy alloy coatings, laser cladding technology was used to fabricate coatings on a G10450 steel substrate, followed by ultrasonic impact treatment (UIT) and recovery treatment (HR, 300 °C). The results showed that the Al₂FeCoNiCrW_0.5 high-entropy alloy coating consisted of BCC and FCC phases. Ultrasonic impact treatment slightly broadened the XRD diffraction peaks, while the recovery treatment had minimal effect on them. Ultrasonic impact also refined the coating grains. Ultrasonic impact treatment increased the coating hardness from 738 HV_0.5 to 856 HV_0.5. Although the subsequent post-annealing slightly reduced the hardness to 806 HV_0.5, it significantly improved wear resistance, with wear loss decreasing from 3.273 mm³ to 2.881 mm³, representing a 15% reduction in wear rate. The improvement in wear resistance was attributed to a change in the wear mechanism of the high-entropy alloy coating. Before and after post-annealing, the mechanism transitioned from abrasive wear, adhesive wear, and oxidative wear to primarily abrasive wear and oxidative wear. Additionally, the recovery treatment transformed the surface from hard and brittle to ductile and resilient.