Abstract
The isothermal oxidation behavior of sintered IN-100 superalloy containing 1 mass% dispersoids of Y2O3 and La2O3 in air at 1273 K was investigated. Atomized IN-100 alloy powders were mixed with Y2O3 or La2O3 powders in a disc-mill under an argon atmosphere and hot-pressed. The particle shape and microstructure of the disc-milled powders resembled very closely to those of mechanically alloyed powder.
Y2O3 dispersion reduced the oxidation rate of sintered IN-100 alloy more markedly than La2O3 dispersion. La2O3 dispersion reduced the oxidation rate slightly, but it intensified the scale adhesion more effectively than Y2O3 dispersion.
EPMA observation of the scale revealed that the scale generally consisted of Cr2O3 layer and internally oxidized layer of Al2O3. The amounts of Ti and Ni in the Cr2O3 layer were higher in the straight alloy than in these dispersion alloys. The scale formed on the Y2O3 dispersion alloy, which showed the smallest mass gain by oxidation, consisted of the outer most layer of TiO2, the Cr2O3 intermediate layer containing almost no Ti, and the Al2O3 inner layer.
