High Temperature Oxidation Resistance of NiCoCrAl High Entropy Alloy Coating on the TiAl Alloy

The high entropy alloy coating is considered as one of the most promising methods to improve the high-temperature oxidation resistance of titanium aluminum alloys due to its fine mechanical property and thermal stability. However, the high entropy alloy coating prepared so far has poor coating quality, and low coating forming efficiency and there are certain requirements for the substrate alloys. To this end, a NiCoCrAl high entropy alloy coating was developed using the double glow plasma alloying technique on the TiAl alloy. The morphology, phase structure, and high temperature oxidation resistance of the coating were comprehensively studied. The results indicate that a uniform and dense coating with a single solid solution of face-centered cube phase formed on the alloy surface. Furthermore, isothermal oxidation test was performed, and the oxidation failure process of the TiAl substrate and the NiCoCrAl-coated sample with different oxidation times was analyzed. It is found that the coating efficiently prevented the TiAl alloy from degeneration for up to 100 h at 900 °C.