Effect of Y2O3 on microstructure and properties of CoCrFeNiTiNb high entropy alloy coating on Ti–6Al–4V surface by laser cladding

Abstract

The effects of Y2O3 on the microstructure, microhardness, wear resistance, high-temperature oxidation resistance, hot corrosion resistance, and electrochemical corrosion behaviour of CoCrFeNiTiNb high entropy alloy coatings formed on Ti–6Al–4V alloy surfaces were studied. The results show that the addition of Y2O3 changes the proportion of the phase but does not change its type. The average grain size is only 1/4.7 of that of the high entropy alloy (HEA) coating, and the fine-grained strengthening leads to increases in the microhardness and wear resistance of 21.8% and 26.9%, respectively. The addition of Y2O3 enhances the denseness and bonding properties of the oxide and corrosion product layers, reducing the oxidation and hot corrosion rates by 60.3% and 40.3%, respectively. The addition of Y2O3 doubles the corrosion resistance which is attributed to the refinement of the grains, the increased proportion of HCP and TiN, and the weakening of galvanic coupling corrosion.