The effect of heat-treatment on microstructure, wear resistance, and corrosion resistance of laser cladding AlCoCrFeNi2.1 high entropy alloy coating

This study details the synthesis of an AlCoCrFeNi2.1 high entropy alloy via laser cladding. The specimens are treated by heating them to 800 degrees C, 1000 degrees C, 1200 degrees C, and 1300 degrees C, respectively, holding them for an hour, and then cooling them in water. The purpose of the study is to explore the effect of high temperature heat treatment on the microstructural evolution and mechanical properties of the alloy. FCC + BCC dual phase microstructure was present in the samples before and after heat treatment. The microstructure was refined first, and then coarsened, as the temperature rose from 800 degrees C to 1300 degrees C. New BCC phase appeared in the initial FCC grains after treated at 800 degrees C, 1000 degrees C, and 1200 degrees C, and no new BCC phase was found in the coating heat treated at 1300 degrees C. Differences in the diffusion rates of Al, Co, Cr, Fe, and Ni atoms at elevated temperatures leads to an increase in size of the newly precipitated phases. The precipitation of BCC phase during high-temperature heat treatment is promoted by the significant negative mixing enthalpy between Al and Ni. At the optimal heat treatment temperature of 800 degrees C and 1000 degrees C, respectively, the sample exhibits optimal hardness and wear resistance. Its corrosion performance is also optimized at this temperature. Fatigue wear, bonding wear, oxidation wear, and abrasive wear are the wear mechanisms of as deposited and heat-treated samples. BCC phase, which is rich in Al & Ni, shows lower corrosion resistance and is preferentially corroded.