Abstract
A low-diffusion NiRePtAl coating ((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer) was prepared on a Ni3Al-base single crystal (SC) superalloy via electroplating and gaseous aluminizing treatments, wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt. In order to perform a comparison with conventional NiAl and (Ni,Pt)Al coatings, the cyclic oxidation performance of the NiRePtAl coating was evaluated at 1100 and 1150 °C. We observed that the oxidation resistance of the NiRePtAl coating was significantly improved by the greater presence of the residual β-NiAl phase in the outer layer and the lesser outward-diffusion of Mo from the substrate. In addition, the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate, where the thickness of the second reaction zone (SRZ) in the substrate alloy decreased by 25 %. The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed, in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.
Published Version
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