High-entropy alloy coatings with excellent mechanical, corrosion resistance and magnetic properties prepared by mechanical alloying and hot pressing sintering

The microstructures and microhardness, wear resistance, corrosion resistance, and magnetic properties of CoCrFeNi and CoCrFeNiCu high entropy alloy coatings (HEACs) prepared by mechanical alloying (MA) and vacuum hot pressing sintering (VHPS) technique on Q235 substrate were studied in detail. Results show that the final milling products are the single face-centered cubic (FCC) solid solution phase for both as-milled HEA powders. The VHPS-ed CoCrFeNi HEAC consists of a single FCC phase, presenting a uniform distribution of principal elements. However, duplex FCC phases are found for CoCrFeNiCu coating with severely component segregation of Cu element. Both HEACs bear a good metallurgical bonding with the substrate. Compared with Q235 substrate, it indicates the higher hardness, superior wear and corrosion resistance in the 3.5% NaCl solution for the two VHPS-ed coatings. Moreover, the microhardness of CoCrFeNi HEAC reaches 450 HV, which is about 12.5% higher than that with Cu addition. And it even displays more excellent wear resistance under the same conditions. Besides, the average corrosion rates in potentiodynamic polarization measurement are greatly reduced for both HEACs, indicating a good corrosion resistance. The magnetization loops show that CoCrFeNi HEAC possesses a good soft magnetic property, however, Cu addition HEAC shows a typical paramagnetic property.