Ultrasonic suppression of element segregation in gas tungsten arc cladding AlCoCuFeNi high-entropy alloy coatings

The excellent mechanical and corrosion properties make high-entropy alloys (HEA) be promising structural and coating materials. However, problems like element segregation hinder the fabrication and application of HEA. Ultrasonic melt treatment (USMT) generally has the effect of segregation suppression. In the present study, the impact of ultrasonic treatment on the microstructure, segregation, mechanical properties, and corrosion properties of AlCoCuFeNi HEA coatings prepared by gas tungsten arc (GTA) cladding on low-carbon substrates are examined and discussed. It was found that the coatings with and without ultrasonic treatment both have BCC dendrites and FCC interdendrites. Ultrasonic treatment increases phase fraction of BCC and narrow secondary dendrite arm spacing (SDAS), thereby increasing hardness, elastic modulus, and room-temperature creep resistance. Ultrasonic treatment suppresses dendritic segregation, thereby improving corrosion properties in 3.5 wt% NaCl solution. According to analysis, acoustic streaming has a greater impact compared with cavitation, which accelerates flow velocity and increases the cooling rate. This study preliminarily examines the effectiveness of ultrasonic treatment in suppressing segregation in HEA.