Effects of ultrasonic impact treatment on structures and properties of laser cladding Al0.5CoCrFeMnNi high entropy alloy coatings

In this research, ultrasonic impact treatment was introduced on the surfaces of laser cladding Al0.5CoCrFeMnNi high entropy alloy coatings. The results showed that obvious solidification boundaries with some lamellar cluster and polygonal precipitations generated inside the cladding coatings. After UIT for one time, a thin impacted layer with obvious plastic deformation was formed. When treated for two times, many floccules formed near the surface while with the increase of impact times evident impact tracks were found on the surface of ultrasonic impact layer due to excessive plastic deformation. In addition, original precipitations located along the solidification boundaries were broken into small ones, and the particles inside the matrix were also cracked. The minimum surface roughness and maximum surface hardness of ultrasonic impact layers can be obtained for one impact time. XRD analysis indicated that Al0.5CoCrFeMnNi cladding coating was composed of single FCC phase while application of UIT technology did not change the phase structure of coatings. It also was noted that the weight losses of ultrasonic impact layers were lower than those of cladding coatings whilst the current density was decreased by 69.6%, 87% in the 3.5%NaCl and 1 mol/L NaOH solutions, respectively, indicating better corrosion resistance of impact layers.