High-temperature steam oxidation behavior and failure mechanisms of Al alloyed Cr coatings on Zr-4 alloy

In this work, the Al content-dependent microstructure evolution and oxidation behavior of co-sputtered CrAl alloyed coatings on Zr-4 alloy were systematically investigated in 1000 ℃ steam. Experimental results demonstrated that the microstructure of generated oxide scale transformed from a Cr2O3 oxide layer with embedding discrete α-Al2O3 particles at low Al contents to a continuous outer (α, θ)-Al2O3 and inner Cr2O3 bi-oxide layer at high Al contents. However, there appeared a unique eutectoid-like Cr2O3/α-Al2O3 multilayered oxide scale in Cr-18.3Al coating, which conferred the sample with optimal oxidation resistance. The underlying oxidation mechanisms were rationalized by revealing the Al content dominated selective oxidation behavior.