The isothermal oxidation behavior of sintered IN-100 superalloy containing 1 mass% dispersoids of Y
2O
3 and La
2O
3 in air at 1273 K was investigated. Atomized IN-100 alloy powders were mixed with Y
2O
3 or La
2O
3 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.
Y
2O
3 dispersion reduced the oxidation rate of sintered IN-100 alloy more markedly than La
2O
3 dispersion. La
2O
3 dispersion reduced the oxidation rate slightly, but it intensified the scale adhesion more effectively than Y
2O
3 dispersion.
EPMA observation of the scale revealed that the scale generally consisted of Cr
2O
3 layer and internally oxidized layer of Al
2O
3. The amounts of Ti and Ni in the Cr
2O
3 layer were higher in the straight alloy than in these dispersion alloys. The scale formed on the Y
2O
3 dispersion alloy, which showed the smallest mass gain by oxidation, consisted of the outer most layer of TiO
2, the Cr
2O
3 intermediate layer containing almost no Ti, and the Al
2O
3 inner layer.
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