Effect of Shot Peening of Substrate Surface on Cyclic Oxidation Behavior of Sputtered Nanocrystalline Coating
In addition to changing the surface roughness of the superalloy,the substrate surface treatment can also modify the microstructure of the surface,which affects the high-temperature oxidation behavior of the high-temperature protective coating.However,there are few reports about the effect of su-peralloy surface treatment on the oxidation behavior of nanocrystalline coatings.In this work,nanocrystal-line coatings were sputtered on the nickel-based single crystal superalloy after two different surface treat-ments of polishing and shot peening,and their cyclic oxidation behavior at 1100℃ was investigated.The phase composition and microstructure of nanocrystalline coatings were characterized by SEM,XRD,and EDS.The results indicated that the cyclic oxidation kinetics of both nanocrystalline coatings at 1100℃ were similar.A dense oxide film could be formed on the surface of nanocrystalline coatings,showing ex-cellent oxidation resistance.However,the microstructure evolution of the interface between the nanocrys-talline coating and shot-peened superalloy substrate differed from that between the nanocrystalline coat-ing and polished superalloy substrate.The sustained formation of the γ′ phase in the nanocrystalline coat-ing near the polished substrate/coating interface was observed during high-temperature oxidation.This phenomenon was not found at the nanocrystalline coating near the shot peened substrate/coating inter-face,while the continuous growth of the γ'phase was observed at the substrate.
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