Microstructure and high temperature properties of laser cladded WTaNbMo refractory high entropy alloy coating assisted with ultrasound vibration

WTaNbMo refractory high entropy alloy (RHEA) coating was prepared by laser cladding with and without ultrasonic vibration assisted on Inconel 718 supperalloy substrate. The effect of ultrasonic vibration on the microstructure, grain size, microhardness, residual stress and high temperature tribological properties at 25 °C, 600 °C, 800 °C and 1000 °C were investigated. The results showed that the ultrasonic vibration improved the homogeneity of microstructure. The coatings were composed of WTaNbMo and γ-(Ni, M) two phases. Under ultrasonic vibration assisted, the average grain size of the coating decreased from 0.48 µm2 to 0.30 µm2, but inversely, the micohardness increased from 753 HV0.5 to 980 HV0.5. The ultrasonic vibration also decreased the residual stress in the coating. In addition, the friction coefficients and wear rates were decreased 10.7 %, 25 %, 25 %, 33 % and 15 %, 20.1 %, 36.2 %, 40.3 % at 25 °C, 600 °C, 800 °C, 1000 °C, respectively. The wear mechanisms and oxides reactions of the coatings at the test wear temperatures were also analyzed.