Investigate on microstructural evolution and oxidation resistance of NiCrAlY coatings at 1 050 ℃
NiCrAlY coating was deposited on Ni-based superalloy substrate using arc ion plating(AIP)technology and then was subjected to isothermal oxidation in air at 1 050 ℃ for up to 200 h with the purpose of further investigating the microstructural evolution during high-temperature oxidation and analyzing the in-trinsic mechanism between the microstructure and oxidation resistance performance,which can provide the-oretical and data references for the development of new high temperature resistant and long-life coatings.The microstructure evolution and high-temperature oxidation resistance mechanism of NiCrAlY coating during the oxidation process were investigated by scanning electron microscopy,X-ray diffraction and X-ray energy spectrometry.The results revealed that vacuum heat treatment could effectively improve the coating struc-ture and homogenize the composition.The α-Al2O3 and Cr2O3 formed during the oxidation process could re-duce the oxidation rate of the coating and inhibit the formation of NiCr2O4 spinel harmful phases,prolonging the service life of NiCrAlY coating.The concentration of Al element in the near-oxide scale side of the coat-ing was reduced with the further oxidation process,leading to the formation of non-protective oxides,which made the oxide scale flake off and reduced the oxidation resistance of the coating.The oxide scale was com-posed of a loose thicker outer oxide layer and a dense thinner inner oxide layer and the curve of coating weight gain with oxidation time followed a parabolic law.The average oxidation rate of NiCrAlY coating af-ter oxidation was 0.085 6 g·m-2·h-1.The research could provide theoretical and experimental data refer-ence for in-depth understanding of the mechanism of high temperature oxidation resistance and the develop-ment of new coatings.
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