Effect of rare earth Y on oxidation behavior of NiAl-Al2O3

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 degrees 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 alpha-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 theta-alpha transformation of Al2O3 is retarded and the formation of voids and cracking are reduced.