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

Abstract

This study details the synthesis of an AlCoCrFeNi_2.1 high entropy alloy via laser cladding. The specimens are treated by heating them to 800 °C, 1000 °C, 1200 °C, and 1300 °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 °C to 1300 °C. New BCC phase appeared in the initial FCC grains after treated at 800 °C, 1000 °C, and 1200 °C, and no new BCC phase was found in the coating heat treated at 1300 °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 °C and 1000 °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.