High-temperature and interfacial oxidation of MAX phase-reinforced composite coatings deposited by laser cladding on Zr alloy substrates

Abstract

MAX phase-reinforced composite coatings were successfully prepared by laser cladding in-situ reaction using TiAl–TiC–Al powder preset on R60702 zirconium alloy surface. The behavior of composite coatings under high-temperature oxidation and interfacial oxidation was investigated. Differential thermogravimetry (DTG) oxidation weight gain curves demonstrated that high-temperature oxidation resistance of composite coating was better than that of Zr alloy. Oxide phase of composite coating mainly contained TiO2 and small amount of Al2O3. Oxidation characteristics of carbides (TiC and Ti2AlC) and TiAl intermetallic compounds revealed that oxidation rates of carbides were higher than those of TiAl intermetallic compounds. In addition, reasons for their different diffusion or oxidation rates were also discussed from the perspective of stability of original microstructure before and after oxidation. At the highest experimental temperature (1100 °C), oxide film thickness of composite coating (20 μm) was smaller than that of Zr alloy (550 μm). Interfacial oxidation behavior indicated that there was bimetallic galvanic corrosion effect between composite coating and Zr alloy, which is related to high electronic energy level of Zr from the perspective of quantum mechanics.