Isothermal aging of a γ′-strengthened Co–Al–W alloy coated with vacuum plasma-sprayed MCrAlY bond coats

Terberger, Philipp; Webler, Ralf; Göken, Mathias; Sebold, Doris; Klein, Leonhard; Ziener, Marco; Virtanen, Sannakaisa; Neumeier, Steffen; Vassen, Robert

doi:10.1016/j.surfcoat.2015.06.048

Journal Article

FZJ-2015-05706

Isothermal aging of a γ′-strengthened Co–Al–W alloy coated with vacuum plasma-sprayed MCrAlY bond coats

Terberger, P. (Corresponding author)FZJ* ; Sebold, D.FZJ* ; Webler, R. ; Ziener, M. ; Neumeier, S. ; Klein, L. ; Virtanen, S. ; Göken, M. ; Vassen, R.FZJ*

2015
Elsevier Science Amsterdam [u.a.]

Surface and coatings technology 276, 360 - 367 (2015) [10.1016/j.surfcoat.2015.06.048]

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Please use a persistent id in citations: doi:10.1016/j.surfcoat.2015.06.048

Abstract: Cobalt-based superalloys with a γ/γ′ microstructure were discovered in 2006 and are currently being investigated as an alternative to nickel-based superalloys for high-temperature, high-load applications in gas turbine blades. They promise a better castability combined with a similar creep strength. Superalloy turbine blades are commonly coated with oxidation resistant bond coats. For this reason their compatibility needs to be studied. Co–9Al–9W specimens with a γ/γ′ microstructure were coated with either a nickel-based or cobalt-based MCrAlY bond coat using vacuum plasma spraying. After aging at 900 °C in air for up to 500 h no decomposition of the γ′ phase was found in the bulk superalloy. The interdiffusion zone shows several different W-rich topologically close-packed phases arising from the dissolution of the γ′ phase in this region. The W-rich phases are identified to be μ phase for both bond coats and R phase for the nickel-based bond coat only. Their total volume is higher for the nickel-based bond coat. Therefore the cobalt-based bond coat is better suited for the Co-based superalloy substrate. Room temperature hardness and Young's modulus were measured using nanoindentation in the initial state and after heat treatment. A significantly higher Young's modulus was found for the cobalt-based bond coat.

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