Abstract: The corrosion behavior of the modified Ni based alloy INCONEL 740,exposed to the simulated coal-ash/flue-gas environments in the combustion furnace,at 750 ℃,has been studied by using SEM,EDX and so on.The results indicate that the corrosion of the modified alloy could be divided into two stages.During the initial stage,with the formation of protective Cr2O3 thin film on the alloy surface,the main corrosion form were oxidation and sulfidation.The corrosion was aggravated when the corrosion continued to 5 000 h.The dissolutions of Co and CoO in the molten salt of the alloy surface played important role in corrosion propagation.It is obvious that the internal sulfidation corrosion took place throughout the whole corrosion process.The sample with lower Fe content exhibited better corrosion resistance to coal-ash/flue-gas compared to the sample with lugher Fe content.