Behaviour of Al, Co, Cr, Ni-based high entropy alloys under high-temperature thermal shock oxidising conditions

This study aims to comprehensively determine the behaviour of Al,Co,Cr,Ni-containing high entropy alloys, i.e. Al25Co25Cr25Ni25, Al20Co25Cr25Ni25Si5 and Al9.1Co18.2Cr18.2Fe18.2Ni36.3 (at%), in high-temperature oxidising atmospheres under thermal shock conditions. In each case, significant mass loss was not determined, indicating very good scaling-resistance. Investigations on the morphology, chemical and phase composition of the alloys after the oxidation process indicate that Cr2O3 is mainly responsible for the good protection, along with Al2O3 in the first two cases. The sample with the highest aluminium content in its scale is Al20Co25Cr25Ni25Si5. Consequently, this material seems to demonstrate the best oxidation properties among the studied alloys.