HIGH TEMPERATURE HOT CORROSION OF NiAl-20%Fe WITH ITS SURFACE ALUMINIDE COATING

The behaviours of high temperature hot corrosion of NiAl, NiAl-20%Fe (atom fraction) without and with aluminized coating in the presence of Na_2SO_4 film at 950℃in air were conducted. NiAl alloy shows hot corrosion resistance to some extent by the formation of Al_2O_3 scale. But, the cracking and dissolution of Al_2O_3 scale may cause its rapid hot corrosion. Additives of 20%Fe may deteriorate the hot corrosion resistance owing to the absence of an Al_2O_3 scale. Aluminizing treatment may improve corrosion resistance of NiAl-20%Fe by promoting the formation of an Al_2O_3 scale. NiAl-20%Fe with aluminide coating has slower corrosion rate than NiAl alloy, which may be attributed to that the aluminide coating has higher Al content, and the Al_2O_3 scale in coating has better cracking resistance than NiAl alloy.