Structure and Oxidation Behavior of a Chromium Coating on Zr Alloy Cladding Tubes Deposited by High-Speed Laser Cladding

A dense and continuous Cr coating with a thickness of approximately 140 μm was successfully deposited on the surface of a thin-walled Zr alloy cladding tube using high-speed laser cladding technology in this study. The microstructure, phase composition, microhardness, and resistance to high-temperature oxidation of the coating were investigated. The experimental results showed that the Cr coating exhibited high-strength metallurgical bond with the Zr alloy substrate, forming a narrow heat-affected zone with a thickness of 25 μm, and the coating consists of ZrCr₂ and α-Zr phase. The average microhardness of the coating was 589 HV_0.05, about 2.3 times that of the substrate. After oxidation at 1200 °C for 1200 s in air, with the formation of complete and dense protective Cr₂O₃ scale, the Cr-coated Zr alloy cladding tube showed better high-temperature oxidation resistance than uncoated tube.