Low Temperature Hot Corrosion Properties of NiAl-31Cr-3Mo Alloy

The low temperature hot corrosion behavior of NiAl-31Cr-3Mo alloy was investigated under constant temperature condition of 550 ℃,600 ℃,650 ℃ and 700 ℃.The microstructure of NiAl-31Cr-3Mo alloy before and after the low temperature hot corrosion were analyzed by means of optical microscopy(OM),SEM and TEM,and the mechanism of low temperature hot corrosion was discussed.There was an incubation period at the initial stage of hot corrosion.The continuous layers of Al2O3 and Cr2O3 were formed on the surface of NiAl-31Cr-3Mo alloy which provided protective effect at 550~650 ℃.At 650~700 ℃,the hot corrosion became serious,cavities were observed in the alloy surface,indicating pitting corrosion occurred,and the basic condition for the acid corrosion of Al-poor,Cr-poor and Mo-rich phases appeared.