Effect of Recovery Treatment on the Microstructure and Tribological Properties of Ultrasonic Impacted Al2FeCoNiCrW0.5 High-Entropy Alloy Coatings

To investigate the effect of recovery treatment on the microstructure and tribological properties of ultrasonic impact-treated Al2FeCoNiCrW0.5 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 Al2FeCoNiCrW0.5 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 HV0.5 to 856 HV0.5. Although the subsequent post-annealing slightly reduced the hardness to 806 HV0.5, 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.