Date of this Version
Materials at High Temperatures 2016 VOL. 33 NOS. 4 & 5
The 1100 °C cyclic oxidation performance of 25 Ni-base commercial and developmental alloys was compiled from an extensive database and ranked according to the 200 h weight change. Cyclic oxidation performance of superalloys is directly controlled by composition. These conventionally cast superalloys were composed of base elements [Ni–Co–Cr–Al], refractory elements [Nb–Mo–Ta–W], oxygen-active elements [Ti–Zr–Hf], light elements [B,C], and occasionally [V–Mn–Si], with P and S trace impurities. The oxidation results were broadly categorised as less than 4 mg/cm2 weight loss for alloys with high 5–6% Al and 3–9% Ta, and with low ≤ 1% Ti (wt.%). Conversely, weight loss of 200–300 mg/cm2 characterised alloys containing low < 3.5% Al, no Ta, and high > 3% Ti. These trends correlated with beneficial and detrimental scale phases previously reported. An unambiguous Cr effect was masked because of its strongly coupled, but inverse, correlation with Al. Multiple linear regression was used to fit alloy composition to a simple logarithmic weight change transform. The function contained 10 terms and yielded a correlation coefficient, r2, of 0.84. Various graphical representations helped to further illustrate, quantify, and predict complex oxidation effects within a 10-element compositional space.