High-temperature oxidation behavior of CeO₂-doped MAO coatings on TC4 titanium alloy

To improve the surface micropores and high-temperature oxidation resistance of micro-arc oxidation (MAO) coatings on TC4 titanium alloy, cerium dioxide (CeO₂) particles were introduced into the electrolyte to prepare MAO composite coatings with different cerium dioxide contents. An X-ray diffractometer, a scanning electron microscope and a multifunctional material surface performance tester were used to analyze the phase composition, surface morphology and bonding force of the samples, respectively. The TC4 substrate, undoped MAO sample and optimally doped MAO sample were oxidized at 650, 750 and 850°C, respectively. The results show that the best-doped MAO samples show excellent high-temperature oxidation resistance at the three temperatures. Compared with the maximum oxidation weight gain per unit area of the undoped MAO sample, that of the optimally doped MAO sample decreased by 10.8, 19.6 and 22.1%, respectively. This is mainly because the thickness, hardness and adhesion of MAO coatings are all increased by doping cerium dioxide particles, and a dense protective layer can also be formed on the surface of the TC4 substrate. The invasion of the oxygen medium is effectively prevented. In this research work, the optimal addition amount of cerium dioxide is 6 g/l.