IMPROVEMENT OF THE HIGH-TEMPERATURE OXIDATION RESISTANCE OF ZR ALLOY CLADDING BY SURFACE MODIFICATION WITH ALUMINUM-CONTAINING TERNARY CARBIDE COATINGS

摘要

Alumina-forming MAX phase ternary carbides are being considered as protective coatings on zirconium alloys as accident tolerant fuel (ATF) cladding because of their resistivity against high-temperature steam oxidation during accident scenarios. This study attempted to synthesize three types of Al-containing MAX phase carbides (Ti_2AlC. Cr_2AlC and Zr_2AlC) as coatings on Zircaloy-4 substrates via deposition of elemental nanoscale multilayer thin films using magnetron sputtering, and subsequent thermal annealing in argon. Formation of Ti_2AlC and Cr_2AlC MAX phases was confirmed after annealing at 800°C and 550°C, respectively, while growth of Zr(Al)C carbide rather than Zr_2AlC MAX phase was observed in the Zr-C-Al system. Oxidation of the three coated samples at 1000°C in steam for 1 hour revealed no protective effect of the Ti_2AlC and Zr(Al)C coatings with significant spallation and cracking. The Cr_2AlC coatings possess superior oxidation resistance and self-healing capability with a thin and dense α-Al_2O_3 layer growth on the surface, which shows good promise as a candidate for coated ATF claddings.