Effect of Tantalum Addition on High Temperature Oxidation Resistance Mechanism of Ni-5Al and Ni-10Al Alloys

Ni-based high-temperature alloys with different mass fractions (0-7%) of tantalum were prepared by powder metallurgy based on the composition of Ni-5Al and Ni-10Al alloy, and the effect of tantalum addition on the high temperature oxidation mechanisms of two alloys was investigated by 1 100℃×100 h high temperature oxidation test. The results show that oxidation mass gain per unit area of Ni-10Al alloy with the same content tantalum was higher than that of Ni-5Al alloy. The addition of tantalum promoted the growth of NiO and the formation of NiTa₂O₆ in the oxide film of Ni-5Al alloy; as the oxidation went on, the oxide layer composed of Al₂O₃ and NiAl₂O₄ formed at the NiO/matrix interface, which hindered the further oxidation of the alloy. The oxide film on surface of Ni-10Al alloy with tantalum consisted of a dense NiO oxide layer on the outside and a loose oxide layer on the inside composed of NiO, Al₂O₃, NiAl₂O₄ and NiTa₂O₆; there were fine holes in the inner oxide layer; the low high temperature oxidation resistance of the alloy was related to the loose oxide film, and formation of defects and NiTa₂O₆ in the oxide film.