Effect of ultrasonic impact coverage on microstructure and properties of laser cladding CrCoNi medium-entropy alloy coating

To investigate the effect of varying ultrasonic impact coverage rates on the wear and corrosion resistance of CrCoNi coatings, a CrCoNi medium-entropy alloy (MEA) coating was fabricated on a 316L substrate via laser cladding, followed by ultrasonic impact treatment (UIT). The microstructure, microhardness, friction and wear performance, and corrosion resistance of the coatings were tested and analyzed at different UIT coverage rates. The results revealed that when the impact amplitude was 20 μm and the coverage rate was 200 %, the coating exhibited the most significant changes in thickness and grain size, resulting in optimal performance. Regarding wear resistance, the wear performance improved initially and then declined as the coverage rate increased, with the minimum wear mass loss and the lowest friction coefficient observed at a coverage rate of 200 %. In terms of corrosion resistance, the CrCoNi coating displayed a higher self-corrosion potential and a lower self-corrosion current density. The equivalent circuit fitting data indicated the formation of a more stable and uniform passive film, which contributed to enhanced corrosion resistance.