Influences of Superalloy Composition and Pt Content on the Oxidation Behavior of Gamma–Gamma Prime NiPtAl Bond Coatings

J. A. Haynes, K. A. Unocic, M. J. Lance, B. A. Pint

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18 Scopus citations

Abstract

The effects of superalloy composition and Pt content on the high-temperature oxidation behavior of γ–γ’ NiPtAl diffusion coatings were investigated over the temperature range of 1050–1150 °C. Simple NiPtAl diffusion coatings with 7 or 12 µm electroplated Pt thickness were evaluated in 1-h cycles in dry O2 for up to 2500 cycles on four superalloys: directionally solidified (DS) alloy 142, 1st generation single-crystal (SX) alloy 1483, and 2nd generation SX alloys X4 and N5. Coatings on high-Hf alloy 142 experienced severe internal oxidation of Hf at all temperatures. Coatings on ~5 at.% Ti alloy 1483 were protective at 1050 °C, but exhibited severe scale spallation at 1100 °C, with extensive formation of Ti- and Ni-rich oxides at the gas interface. Coatings with 7-µm Pt on X4 were extremely protective at 1100 °C, but failed rapidly at 1150 °C, which also was associated with the formation of Ti-rich oxides. Increasing the coating Pt content on X4 improved the 1150 °C oxidation behavior. Coatings on Ti-free N5 showed the best performance at 1150 °C, especially with 12-µm Pt. Although γ–γ’ coatings can exhibit outstanding cyclic oxidation resistance with minimal Al depletion, they appear to be sensitive to substrate composition, as well as eventual Pt depletion due to interdiffusion.

Original languageEnglish
Pages (from-to)453-481
Number of pages29
JournalOxidation of Metals
Volume86
Issue number5-6
DOIs
StatePublished - Dec 1 2016

Funding

The authors would like to thank G. Garner, T. Jordan, T. Lowe, and D. Leonard, for assistance with the experimental work. Capstone Turbine Corp., Siemens, General Electric Aircraft Engines, and Howmet provided the superalloys for these experiments and Prof. Y. Zhang at TTU assisted with the Pt plating. M. Brady and S. Dryepondt provided helpful comments on the manuscript. This research was sponsored by the U.S. Department of Energy, U.S. Assistant Secretary for Energy Efficiency and Renewable Energy, and Advanced Manufacturing Office (Combined Heat and Power Program).

Keywords

  • Bond coating
  • Diffusion coating
  • Gamma prime
  • High-temperature oxidation
  • Platinum

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