High-temperature oxidation resistance and antifailure mechanism of MAO-SG composite coating on TC4 titanium alloy

To refine microarc oxidation (MAO) coating surface micropores, and enhance the coating's toughness and oxidation resistance. In the process of MAO, negatively charged CeO2 particles are adsorbed and deposited into the coating under the action of electrophoresis, and a 6 g/L CeO2 doped MAO coating is prepared. Then, the Al2O3-SiO2 composite sol-gel seal coating was used to obtain the microarc oxidation-sol-gel composite coating (MAO-SG). The TC4 substrate, undoped MAO coating, CeO2 doped MAO coating, and MAO-SG composite coating were subjected to high-temperature oxidation at 650, 750, and 850 degrees C, respectively. The results show that the composite coating exhibits excellent high-temperature oxidation resistance at three temperatures. Compared with the undoped MAO coating, the maximum oxidation weight gain per unit area of the MAO-SG coating was reduced by 13.44%, 23.87%, and 38.16%, and the average oxidation rate was reduced by 17.15%, 50.98%, and 69.37%, respectively. The sol-gel layer on the surface of the composite coating will decompose alpha-Al2O3 at high temperatures, and form a dense protective layer on the surface of the MAO coating and protect the MAO coating, which greatly improves the high-temperature oxidation resistance of the TC4 titanium alloy.