Microstructures and Wear Resistance of AlCrFeNi2W0.2Nbx High-Entropy Alloy Coatings Prepared by Laser Cladding

Abstract

The AlCrFeNi2W0.2Nbx high-entropy alloy (HEA) coatings were synthesized on the 304 stainless steel by laser cladding. The microstructure, microhardness and wear resistance of HEA coatings were investigated. The HEA coatings show a good metallurgical bonding to the substrate, and they consist of the cladding zone, bonding zone and heat-affected zone. The phase structures of the HEA coatings are the BCC solid solution phase and the Fe2Nb-type Laves phase. The Nb0.5 composition shows a hypo-eutectic microstructure; the primary phase is the BCC solid solution phase. While Nb1.0, Nb1.5 and Nb2.0 coatings show hyper-eutectic microstructures, the primary dendrites show the Laves phase. The microhardness of AlCrFeNi2W0.2Nbx coatings increases with increasing Nb content and that of the Nb2.0 coating is up to 890.7 HV, about 4.5 times as the 304 stainless steel. Dry sliding model wear testing has been performed. The AlCrFeNi2W0.2Nbx (x = 1.5, 2.0) high-entropy alloy coatings exhibit an order of magnitude lower wear than 304 stainless steel under the same loading conditions. It is attributed to the larger volume fraction of hard Laves phase and the anti-attrition of newly formed oxidation films during friction process.