CoCrFeNi(W1 − xMox) high-entropy alloy coatings with excellent mechanical properties and corrosion resistance prepared by mechanical alloying and hot pressing sintering

Abstract

The CoCrFeNiW and CoCrFeNiW0.5Mo0.5 high-entropy alloy coatings (HEACs) have been prepared by mechanical alloying and vacuum hot pressing sintering (VHPS) technique on Q235 steel substrate. The microstructures, microhardness, wear resistance and corrosion resistance of HEACs were studied in detail. The final milling products for as-milled CoCrFeNi(W1−xMox) (x=0, 0.5) coating powders are the mixture of body-centered cubic (BCC) and face-centered cubic (FCC) solid solution phases, while order FCC phase exists for CoCrFeNiW. VHPS-ed CoCrFeNiW and CoCrFeNiW0.5Mo0.5 HEACs are 600 and 650μm in thickness respectively, and bear a good metallurgical bonding to the substrate. Both HEACs comprise two FCC phases with a small amount of δ-NiW and σ-CoCr phases. The average microhardness values of CoCrFeNiW and CoCrFeNiW0.5Mo0.5 HEACs reach 669 and 600HV respectively, which far exceed the substrate (160HV). And both coatings exhibit superior wear resistance than substrate under the same wear conditions. The corrosion resistance in 3.5% NaCl solution of the coatings is improved compared with substrate. Especially, Mo addition remarkably enhances corrosion resistance as reflected by the lowest corrosion current density and more positive corrosion potential as well as a reduction in average corrosion rate.