Role of nitrogen and tantalum in the high-temperature oxidation behavior of AlCoCr 0.5 NiTa x Ti(N) alloys synthesized by laser in situ synthesis

Laser cladding was used to synthesize the coatings of the AlCoCr 0.5 NiTa x Ti (N) alloys on a Ti-6Al-4 V substrate. As the Ta content increased, the alloy evolved from columnar crystals composed of dendritic face -centered cubic (FCC)/L1 2 phases and interdendritic Laves phases to a eutectic structure. The high -valence state of Ta diminished oxygen vacancies in TiO 2 , which reduced the diffusion rate, so an appropriate Ta content improved hightemperature oxidation resistance. In the cladding process, nitrogen from the protective gas was partially dissolved in the alloy and partially formed Ti 2 N, both of which act as diffusion barriers for titanium, inhibiting the formation of titanium oxide and promoting the formation of continuous single aluminum oxide, thereby improving oxidation resistance at high temperatures.