Salt-deposit hot corrosion behaviors of directionally solidified DZ466 superalloy

Hot corrosion behaviors of DZ466 alloy at 850℃ and 950℃ were investigated by using a NaCl/Na₂SO₄salt-deposit method. It is found that there are three corrosion layers on the alloy. The outer and the middle layers consist of(Ni,Co) O oxide and(Ni,Co) Cr₂O₄ with a spinel structure,respectively. The innermost layer is an inner corrosion layer,which consists of Ni₃S₂ at 850℃,and the internal oxidation Al₂O₃ can be produced close to the middle layer at 950℃. The same hot corrosion mechanism is shown at 850℃ and 950℃. The destruction of the oxidation film continuity is a key reason for hot corrosion of the alloy. The hot corrosion weight gain curves obey a parabolic law at the two temperatures,the rate constants are 3.1×10^-11g²·cm^-4·s^-1 and 1.5 × 10^-9g²·cm^-4·s^-1,and the hot corrosion activation energies are 179.2 and 138.3 kJ ·mol-1at 850℃ and 950℃,respectively.