Abstract:In-situ NiAl-Al₂O₃ and Y-doped NiAl-Al₂O₃ were fabricated by mechanical alloying (MA) and pulse current auxiliary sintering (PCAS). The isothermal and cyclic oxidations were carried out at 1 000 °C in order to investigate the influence of Y on the oxidation behaviors of NiAl-Al₂O₃. The results indicate that the addition of Y does not change the oxidation product of NiAl-Al₂O₃ and the α-Al₂O₃ scale is detected on the surface of NiAl-Al₂O₃ and NiAl-Al₂O₃-Y after isothermal oxidation. The addition of Y changes the morphologies of the scale during isothermal oxidation and leads to the disappearance of the ridge structures. Meanwhile, the mass gain of NiAl-Al₂O₃-Y is much lower than that of NiAl-Al₂O₃. During cyclic oxidation, the cracking and spallation, which were observed in the scale of NiAl-Al₂O₃, are eliminated with the addition of Y because the θ−α transformation of Al₂O₃ is retarded and the formation of voids and cracking are reduced.

Key words: NiAl; oxidation resistance; rare earth Y