Effects of laser energy density on the resistance to wear and cavitation erosion of FeCrNiMnAl high entropy alloy coatings by laser cladding

FeCrNiMnAl high entropy alloy (HEA) coatings are prepared on the surface of 304 stainless steel (304 SS) by laser cladding. The effects of laser energy density on the residual stress, microstructure, nanoindentation behavior, the resistance to wear, corrosion and cavitation erosion (CE) of FeCrNiMnAl HEA coatings are studied. Experimental results shows that when the laser energy density decreases from 40 J/mm² to 24 J/mm², the phase composition of the FeCrNiMnAl HEA coatings remains unchanged with a single BCC solid solution and the elements are uniformly distributed without obvious segregation. The average grain size of the HEA coatings is refined from 73.5 to 41.7 μm. When the laser energy density is 28 J/mm² for S3 sample, the coating displays good forming quality and excellent comprehensive performance. The specific wear rate is only 8.2 % that of the 304 SS substrate. In addition, S3 exhibits the highest corrosion resistance as indicated by the highest corrosion potential (E_corr) and the lowest corrosion current density (I_corr) in 3.5 wt% NaCl solution. After 10-h CE, the mean depth erosion rate (MDER) of S3 is the lowest (1.69 ± 0.03 μm/h), which is much lower than that of 304 SS (4.96 ± 0.13 μm/h), and the pure mechanical damage plays a dominant role in CE, followed by the synergistic damage effect. The excellent CE resistance of S3 is attributed to its excellent combination of corrosion resistance, mechanical properties and the self-recovery ability of passivation film.