High-performance Cr2AlC MAX phase coatings for ATF application: Interface design and oxidation mechanism

Surface-modified Zr-based alloy (ZIRLO) claddings with advanced ceramic coatings are increasingly required for accident-tolerant fuel (ATF) systems in light-water reactors. Cr2AlC MAX phase coatings are promising for this purpose owing to their remarkable properties combining radiation/oxidation/corrosion resistance. However they are suffering from weak interface compatibility to ZIRLO substrate and poor structural densities for long-term services. Herein, we fabricated densely high-purity Cr2AlC MAX phase coatings with uniquely designed Cr/CrCx interfacial layers. The oxidation behavior of the coatings was focused under steam environments at 1000–1200 °C. Results showed that Cr2AlC coatings exhibited an oxidation mass gain of 8.9 mg/cm2 and an oxide thickness of 680 nm after oxidation at 1200 °C for 30 min, which were about 10% and 0.5% of ZIRLO substrate, respectively. Based on microstructural evolutions, the embedded interfacial layers significantly suppressed the rapid diffusion of Al in Cr2AlC coatings to the substrate and the premature delamination of oxidized coatings. Particularly, the formed oxides were identified as dense yet pure α-Al2O3, which endowed the protection against further oxidation and excellent resistance to high-temperature steam corrosion.