Effect of Al content on the microstructure, properties, and oxidation behaviors at 900 degree celsius of (MoNbCoCrAlxSi0.2)70Ti30 refractory high-entropy alloys coatings fabricated by electron beam cladding

Electron beam cladding (MoNbCoCrAlxSi0.2)70Ti30 RHEAs coatings with different Al contents on the surface of Ti600 alloy, and their microstructure and properties were investigated. Two solid solution phases, A2/B2-BCC1 and A2-BCC2, and precipitated phases (Ti,Mo,Nb,Al)5Si3-IMC were found. The mechanical properties and wear resistance of RHEAs coatings increase and then decrease with increasing Al. The mechanism of the change in mechanical properties and wear resistance is based on the strong and weak relation between solid solution strengthening and precipitation strengthening. The improvement of high-temperature oxidation resistance is due to the promotion of Al2O3 formation at the early oxidation stage.