Diffusional transport and predicting oxidative failure during cyclic oxidation of β-NiAl alloys

✍ Scribed by J.A Nesbitt; E.J Vinarcik; C.A Barrett; J Doychak

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 947 KB
• Volume: 153
• Category: Article
• ISSN: 0921-5093
• DOI: 10.1016/0921-5093(92)90251-u

✦ Synopsis

Nickel aluminides (NiAI) containing 40-50 at.% AI and up to 0.1 at.% Zr have been studied following cyclic oxidation at 1200, 1300, 1350 and 1400 °C. The selective oxidation of aluminum resulted in the formation of protective A1203 scales on each alloy composition at each temperature. However, repeated cycling eventually resulted in the gradual formation of less protective NiA1204. The appearance of the NiAI204, signaling the end of the protective scale-forming capability of the alloy, was related to the presence of ~/-(Ni3AI) which formed as a result of the loss of aluminum from the sample. A simple methodology is presented to predict the protective life of fl-NiAl alloys. This method predicts the oxidative lifetime due to aluminum depletion when the aluminum concentration decreases to a critical concentration. The time interval preceding NiAI204 formation (i.e. the lifetime based on protective AI203 formation) and predicted lifetimes are compared and discussed. Use of the method to predict the maximum use temperature for NiA1-Zr alloys is also discussed.