Effects of targeted γ-Ni + γ′-Ni3Al-based coating compositions on oxidation behavior

✍ Scribed by T. Izumi; N. Mu; L. Zhang; B. Gleeson

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 646 KB
• Volume: 202
• Category: Article
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2007.08.014

✦ Synopsis

The 1150 °C oxidation behavior of γ + γ′-based alloys containing up to 20 at.% Pt and 15-22 at.% Al was investigated in an effort to further develop and optimize alternative bond coating compositions for advanced thermal barrier coating systems. It was found that the co-addition of Pt and Hf was extremely beneficial to oxidation resistance, to the extent that Ni-20Al-20Pt-Hf and Ni-20Al-10Pt-Hf alloys oxidized at significantly slower rates than a Ni-50Al-15Pt β-NiAl alloy. Moreover it was found that there is an optimum Hf content that depends on Pt content in the alloy. A feasible method to deposit Pt + Hf-modified γ + γ′ coatings having overall compositions closely approaching those targeted (Ni-Al 15-20 -Pt 15-20 -Hf) on the basis of the bulk-alloy study was subsequently developed. Cyclic oxidation testing of a representative γ + γ′ coating at 1150 °C in air revealed the absence of surface rumpling and excellent compatibility with the superalloy substrate as major advantages compared to traditional Pt-modified β-NiAl coatings.