Effect of Cu content on microstructure and properties of CoCrFeNiCux high-entropy alloy coatings prepared by induction cladding

CoCrFeNiCux (x = 0, 0.5, 1.0, 1.5) high entropy alloy coating (HEAc) on Q235 steel was successfully prepared by induction cladding technology. Before induction cladding, the final structure of the alloy powders after 30 h ball milling were single-phase face-centered cubic (FCC) structure. After induction cladding, the metastable Cu-containing alloy powders were transformed into a stable dual-phase, that was, Cu-depleted FCC1 and Cu-rich FCC2. It was worth noting that HEAc exhibited a hardness gradient from top to bottom due to the unique principle of induction cladding. With the increase of Cu content, the grain size of HEAc was refined, but the overall hardness and wear resistance of HEAc decreased due to the precipitation of Cu. Grain refinement also provided more channels for oxygen invasion, and the oxidation resistance decreased. The convergence of Cu element at grain boundaries led to local galvanic corrosion, which greatly reduced the corrosion resistance. Therefore, the precipitation of Cu and grain refinement had great influence on the wear resistance, high temperature oxidation resistance and corrosion resistance of HEAc.