预氧化真空度对冷喷涂 CoNiCrAlY 涂层高温氧化行为的影响

A CoNiCrAlY coating was prepared by cold spray and pre-oxidized in a vacuum environment under different vacuum degree. The effect of vacuum degree of pre-oxidation on the oxidation behavior of CoNiCrAlY coatings at 1 050 °C was studied by XRD, SEM and EDS. The results show that the as-sprayed coating presents a dense structure with low porosity (less than 0.36vol%) and low oxygen content (0.12wt%). Vacuum heat treatment improves the density of as-sprayed coating, converts the single-phase (γ) as-sprayed coating to a two-phase γ-Matrix/ β-(Ni, Co)Al microstructure, and forms a continuous, dense and single α-Al₂O₃ layer. During the course of oxidation, the growth rate of TGO formed on CoNiCrAlY coating decreases with the decrease of vacuum degree. When the vacuum degree is less than or equal to 10^-3 Pa, vacuum degree has little influence on the growth rate of TGO. An Al₂O₃ layer with larger grain size and less defect is formed on the surface of pre-oxidized coating during the oxidation process, which can decrease the diffusion area for Al and O. As a result, the growth rate of Al₂O₃ decreases and thus the formation of spinel oxide is suppressed. It is concluded that the oxidation resistance of cold-sprayed CoNiCrAlY coating has been greatly improved by vacuum pre-oxidation treatment.