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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 TiO 2 and small amount of Al 2 O 3. Oxidation characteristics of carbides (TiC and Ti 2 AlC) 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. [ABSTRACT FROM AUTHOR]

In this study, TiC/TiAl composite coatings are prepared on TC4 substrate via laser cladding. The effect of TiC content (5, 10, 15, and 20 vol%) on the microstructure, microhardness, and wear characteristics of the coatings are investigated. The results show that the physical phases in all four coatings are mainly TiAl, Ti 3 Al, TiC, and Ti 2 AlC. The amount of rod-shaped Ti 2 AlC increases and the TiC dendrite orientation is weakened and significantly refined with decreasing TiC content. The hardness of the four coatings is 1.8–2.4 times that of the substrate, with the 15 vol% coating being the hardest (799 HV 1.0). The wear rate of the 5 vol% coating is the lowest, 1.6 times lower than that of the substrate. This is mainly attributed to the heterogeneous structure of the coating composed of Ti-Al substrate, hard TiC particles, and self-lubricating Ti 2 AlC phase. The surface energy of the 5 vol% coating is the lowest, resulting in a very slight material migration from the wear surface, and the wear mechanism is micro-cutting. [ABSTRACT FROM AUTHOR]