External and internal oxidation properties of ternary iron-silicon-aluminum, nickel-chromium-aluminum, and nickel-silicon-aluminum alloys.

摘要

The oxidation properties of binary and ternary Fe-Si-Al alloys containing 0-6 at% Si and 0-6 at% Al were investigated at 1073 K in 0.04-0.07 torr and 760 torr of oxygen. In combination with Si, the Al concentration required to form a protective Al;A criterion has been established for the onset of internal oxidation beneath the external scale when oxidizing conditions favor formation of the oxide of the least noble metal in a dilute ternary alloy. This criterion was applied to the oxidation of ternary Fe-Si-Al and Ni-Cr-Al alloys. Theoretical predictions of minimum Al concentrations required to form a protective Al;Attempts were made to give expressions describing the kinetics of internal oxidation of dilute ternary alloys during simultaneous internal oxidation of the two solutes. Good agreement was obtained between theoretically predicted and experimentally observed values of the depths of internal oxidation zones in Ni-1at%Si-4at%Al alloys at 1073 K in Ni/NiO packs or in 760 torr of oxygen.