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

Abstract

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/CrC_x 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.