Abstract:
CoNiCrAlY coatings were prepared by cold spray process.After deposition,the pre-oxida-tion of the coating was performed by vacuum heat-treatment.The microstructure and phase constitu-ent of coating were characterized by XRD,FE-SEM and TEM.The corrosion behavior and mecha-nisms of as-sprayed and pre-oxidized coatings in molten 75%Na2SO4+25%NaCl(mass fraction,the same below)at 900℃ were also studied.The results show that the as-sprayed coating presents a nanocrystalline structure with low porosity(less than 0.28% volume fraction)and low oxygen con-tent(0.12%).Vacuum pre-oxidation treatment improves the bonding status of particle interface and forms a continuous,uniform and denseα-Al2O3 layer,with an average thickness of 0.26μm.As-sprayed and pre-oxidized coatings can protect the substrate from hot corrosion due to the formation of the continuous and denseα-Al2O3 layer.Moreover,the vacuum pre-oxidation treatment can alleviate the diffusion of S and Cl into coating and thus lead to an increase of one time in the hot corrosion re-sistance than the as-sprayed coatings.
Key words:MCrAlY coating;nanocrystalline;hot corrosion;cold spray;vacuum pre-oxidation
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