High Temperature Corrosion of Ni Based Alloy Inconel 740H in Simulated Coal-ash and Flue-gas Environments

Abstract

The corrosion behavior of the Ni-based superalloy Inconel 740H exposed to synthetic coal-ash/flue-gas at both 750°C and 780°C for 5000h was studied. The microstructures of samples were characterized by using XRD, SEM with EDS. The results indicate that the 740H alloy exhibits stable microstructure after long time aging. The overall corrosion of specimens was divided into two successive stages. In initial stage, the Cr2O3 protective film formed on the surface of the samples and became thicker slowly and had a good adherence to the matrix. In propagation stage, the Cr2O3 was dissolved by the composite sulfate. This resulted in the low temperature hot corrosion of alloy. The corrosion layers were composed of inner sulfide layer, oxide layer and outer loose layer. The alloy corrosion at 780°C was more severe than that of at 750°C.