DYNAMIC OXIDATION OF A CU-30VOL.PERCENT-CR COATING ON A COPPER-BASED ALLOY

A Cu-30vol.%Cr coaling produced by co-evaporation of Cu and Cr was eva luated is an electric arc-heated wind tunnel. The wind tunnel generate d high-velocity, dissociated air containing atomic oxygen. The coating provided good oxidation protection for the copper alloy substrate und er dynamic environment at 650-760 degrees C. The oxide morphologies of the coating under dynamic conditions were distinct from those of stat ic oxidation. The atomic oxygen in the gas stream accelerated the oxid ative evaporation of Cr metal resulting in the formation of a porous l ayer of Cu-oxides on the coating surface. Oxidation resistance of the coating derived from a continuous layer of Cr2O3 formed underneath the external Cu-oxides so that the Cr2O3 scale was shielded from the host ile dynamic oxidation/atomic oxygen environment.