FeCoCrNi-Mo high entropy alloy/diamond composite coatings were successfully prepared by high speed laser cladding. A high scanning speed was adopted (>30 mm/s), and the effects of laser power, scanning speed, and diamond content on the microstructure and wear resistance of the composite coating were studied. The processing parameters of laser cladding had significant influence on the dilution ratio, graphitization of diamond, and wear resistance of the composite coatings. When the laser cladding parameters were 3000 W of laser power and the high scanning speed of 50 mm/s, the composite coating exhibited a uniform microstructure, the lowest dilution ratio, and the best wear resistance. The wear resistance of the composite coating was enhanced with the addition of diamond, but microcracks also increased. When the amount of diamond was 15 wt.%, the best combination of microstructures and wear resistance was obtained.

Introducing the oxidation-resistant coating on Zr alloy is considered to be one of the potential solutions for accident-tolerant fuel (ATF) materials. In this study, pure Cr coatings were prepared on a Zircaloy-4 (Zry-4) alloy surface by multi-arc ion plating under different process parameters. The ability of Cr coating on Zry-4 alloy cladding to improve the oxidation resistance to prevent a loss-of-coolant accident (LOCA) was studied. The microstructure of Cr coating was analyzed using the EBSD technique, and the high-temperature steam oxidation was tested at 800, 1000 and 1200 °C. Compared with the original Zry-4 alloy, the samples with Cr coatings exhibited much better oxidation resistance under different high-temperature steam oxidation conditions. However, the Cr coating exhibited columnar grain, strong preferred orientation and (001) fiber texture. The columnar grain boundaries provided paths for the diffusion of oxygen atoms to the Zry-4 alloy matrix at high temperatures. The results showed that the oxidation film of Cr coating with relatively random grain orientation was compact and uniform and exhibited the best oxidation resistance at high temperatures.