Study on Oxidation Resistance of AlF₃-TiAl Composite Coating by Magnetron Sputtering

TiAl coating and AlF₃-Ti Al composite coating were prepared on TC4 titanium alloy by magnetron sputtering technique, and the isothermal oxidation and non-isothermal oxidation behaviors of the two coatings were investigated by tube furnace and comprehensive thermal analyzer, respectively, and the physical phases, morphology, and elemental distributions of the oxidized films were characterized by X-ray diffraction and scanning electron microscopy, etc. The results show that when the isothermal oxidation is carried out at 800 ℃ for 20 h, the oxidized weight gain of the Ti Al and AlF₃-Ti Al composite coating is 9.23 mg·cm^-3and 5.45 mg·cm^-3, respectively. AlF₃-Ti Al composite coatings show an oxidized weight gain of 9.23 mg·cm^-3and 5.45 mg·cm^-3, respectively, the latter being 40.97% lower than the former. During the non-isothermal oxidation process, when the temperature is ＜500 ℃, the oxidized weight gain and weight gain rate of the two coatings are basically equivalent, but when the temperature is ≥500 ℃, the oxidized weight gain rate of AlF₃-Ti Al composite coating decreases significantly, and the gap between its oxidized weight gain and that of the Ti Al coating increases, and the oxidized weight gain of AlF₃-Ti Al composite coating decreases by 31.18% compared to that of the Ti Al coating at 1200 ℃. The oxidized weight gain of AlF₃-Ti Al composite coating decreases by 31.18% compared to that of the Ti Al coating. The AlF₃-Ti Al composite coating shows more excellent antioxidant performance than Ti Al coating, which is due to the fact that AlF₃ reacts with Al to generate gas-phase Al F in the coating at higher temperatures（＞454 ℃）, which cna promote the generation of Al₂O₃.