The effect of alloy elements on corrosion and oxidative resistance of W-based alloy films

Tungsten is considered as the foremost candidate material for the plasma facing material (PFM) in future fusion device, and excellent high temperature oxidation resistance is the important safety criterion to prevent radioactive pollution in case of a Loss-of-Coolant-Accident (LOCA) with simultaneous air ingress. Recently, high entropy alloys were found to have prominent high temperature oxidation resistance and corrosion resistance. The present paper focuses on the high temperature oxidation resistance of tungsten based high entropy alloy, and their structures and corrosion resistances are also studied. In this study, thin films of W, WTa, WTaCr, WTaCrV, WTaCrVAl, WTaCrVAlTi and WTaCrVAlTiZr were prepared via the magnetron sputtering method with a kind of composed target consisting of fan-shapes. The results show that as the number of selected elements increases, the entropy increases, the disorder of film structure increases significantly resulting in the formation of amorphous structure, and the corrosion resistance and oxidation resistance of the alloys also improve greatly. The further analysis and experiments proved that: one important reason for the improving of corrosion resistance and oxidation resistance is that the increase of mixing entropy reduces the Gibbs free energy of alloys and makes them more chemically stable; another reason is that the elements of Cr, Al, Ti and Zr can promote the formation of dense oxide passive layer.