Hot corrosion behavior of a Si-Y co-deposition coating on a Ti2AlNb based alloy in NaCl-Na2SO4 mixture

Abstract A Si Y co-deposition coating was prepared on a Ti2AlNb based alloy by pack cementation technique. Hot corrosion behavior of this coating covered by a salt mixture composed of NaCl-Na2SO4 at 1023 K was investigated. The results showed that application of the coating remarkably enhanced the hot corrosion resistance of the alloy, but the hot corrosion induced by the salt mixture affected the coating more seriously than mere oxidation in air. During the hot corrosion, the coating formed protective amorphous Na2Si2O5 and effectively prevented ingress of corrosive media into the alloy. However, occurrence of self-sustaining sulfurization/oxidation and chlorination/oxidation reactions should be responsible for the accelerated degradation of the coating. Moreover, escape of gaseous corrosion products created holes in the scale.