Ar-H₂O雰囲気におけるFe-Ni合金の高温酸化

抄録

The oxidation of Fe-(9, 36%)Ni alloys at 1 000-1 400 K has been studied in Ar-(1, 5, 10%)H₂O atmosphere using metallographic and electron probe microanalysis techniques.
The scales consisted of the outer scale and the subscale which had a typical substructure of intergranular oxide zone and a metal/oxide mixed zone. The oxide phase in each scale was identified as FeO. With the increase in Ni content in the alloys the total oxidation rates decreased, but the growth rates of subscale increased.
The oxidation rates and morphologies of the scales did not depend on the partial pressure of H₂O in the range between 1 and 10 percent in Ar gas.
At all the temperatures the subscales grew according to a parabolic rate law, and the apparent activation energies for the processes were estimated to be 129 kJ/mol for Fe-9%Ni alloy at temperature above 1 100K and 111 kJ/mol for Fe-36%Ni alloy at temperature above 1 000 K, respectively. The rate determining diffusion element in these alloys was considered to be Fe in FeO.