High vacuum arc ion plating TiAl coatings for protecting titanium alloy against oxidation at medium high temperatures

High vacuum arc ion plating TiAl coatings are explored for protecting titanium alloys against oxidation at temperatures below 700 °C. Bi-phased TiAl coatings which are composed of γ-TiAl + α2-Ti3Al were obtained under the substrate bias range of 0 V to −350 V, which formed Al2O3-rich oxide layers during oxidation. Higher bias induced slight decrease of Al content but dramatically densified the microstructure of the coating, resulting in improved oxidation resistance of the TiAl coatings. Meanwhile, no detrimental interdiffusion phase was observed after oxidation for 100 h, showing good protectiveness of the TiAl coatings.