NaCl-induced hot corrosion of a titanium aluminide alloy

NaCl-induced hot corrosion of a TiAl-based intermetallic, Ti-47at.%Al-2at.%Nb-2at.%Mn + 7 vol.% TiB2, was studied. Sodium chloride was vapor deposited on the surface of the specimens. The reaction of the metal, oxygen and deposited sodium chloride caused the formation of a non-protective scale and accelerated the oxidation of the alloy. Pits and possible grain boundary attack were observed on the corroded surfaces. Oxygen-free exposure showed no corrosion of the TiAl alloy due to NaCl at temperatures below and above the melting temperature of NaCl. Thermodynamic calculations were carried out to predict the possible corrosion products. The corrosion mechanisms are discussed.