Ar-H₂O雰囲気におけるFe-38Ni-13Co-4.7Nb-1.5Ti-0.4Si耐熱合金の高温酸化

抄録

The oxidation of an Fe-38Ni-13Co-4.7Nb-1.5Ti-0.4Si alloy, Incoloy 909 type alloy (alloy 909), has been investigated in the temperature range of 1000K to 1400K in Ar-(1, 10%)H₂O atmosphere using metallographic, electron probe microanalysis and X-ray diffraction techniques.
The oxide scales consisted of an external scale and an internal scale which had an intergranular scale (> 1200K) and an intragranular scale. The oxide phases in each scale were identified as α-Fe₂O₃(< 1200K) or FeO (> 1300K) and CoO·Fe₂O₃ and FeO·Nb₂O₅, respectively.
The morphologies, the oxide phases and the oxidation rates did not depend on the partial pressure of H₂O in the range between 1 and 10 percent in Ar gas. The rate constants for the intergranular scale formation in alloy 909 were about one-tenth as large as those in Fe-36%Ni alloy reported previously.
At all the temperatures the scales grew according to a parabolic rate law and the apparent activation energies for the processes were estimated.