Laser surface alloying of FeCoCrAlNi high-entropy alloy on 304 stainless steel to enhance corrosion and cavitation erosion resistance

FeCoCrAINi high -entropy alloy coating was synthesized with premixed high -purity Co, Cr, Al and Ni powders on 304 stainless steel by laser surface alloying, aiming at improving corrosion and cavitation erosion resistance. Phase constituents, microstructure and microhardness were investigated using XRD, SEM, and microhardness tester, respectively. The cavitation erosion and electrochemical corrosion behavior of FeCoCrAINi coating in 3.5% NaCl solution were also evaluated using an ultrasonic vibrator and potentiodynamic polarization measurement Experimental results showed that with appropriate laser processing parameters, FeCoCrAINi coating with good metallurgical bonding to the substrate could be achieved. FeCoCrAINi coating was composed of a single BCC solid solution. The formation of simple solid solutions in HEAs was the combined effect of mixing entropy (Delta S-mix), mixing enthalpy (Delta H-mix), atom size difference (delta) and valence electron concentration (VEC), and the effect of Delta S-mix was much larger than that of the other factors. The microhardness of the FeCoCrAINi coating was similar to 3 times that of the 304 stainless steel. Both the corrosion and cavitation erosion resistance of the coating were improved. The cavitation erosion resistance for FeCoCrAINi HEA coating was similar to 7.6 times that of 304 stainless steel. The corrosion resistance was also improved as reflected by a reduction in the current density of one order of magnitude as compared with 304 stainless steel. (C) 2016 Elsevier Ltd. All rights reserved.