Correlation of alloy microstructure with oxidation behavior in chromia-forming intermetallic-reinforced Cr alloys

Abstract

The oxidation behavior of the Cr(X) solid solution and intermetallic Cr2X Laves phases (X = Nb, Ta) was studied individually and in combination at 1,100°C in humid air. The two-phase Cr(Ta) + Cr2Ta alloys exhibited superior oxidation resistance to either the single-phase Cr(Ta) or the single-phase Cr2Ta alloys. However, the two-phase Cr(Nb) + Cr2Nb alloys exhibited lower oxidation resistance than either the single-phase Cr(Nb) or Cr2Nb alloys. The two-phase Cr(Ta) + Cr2Ta alloys were also found to exhibit superior oxidation resistance to the two-phase Cr(Nb) + Cr2Nb alloys. This was hypothesized to be related to the lower amount of the Cr2X phase in the Cr(Ta)–Cr2Ta eutectic and to the lower solubility of Ta in the Cr(X) phase, relative to the Cr–Nb system. Both of these factors resulted in significantly less oxidation and nitridation in the Cr(Ta) + Cr2Ta alloys.