Study on Hot Corrosion Behavior of Ti48Al2Nb2Cr Alloy

Abstract

In order to study the hot corrosion behavior of TiAl alloy and reveal its corrosion mechanism for improving its actual service performance, especially the hot corrosion resistance, the hot corrosion behavior of Ti48Al2Nb2 Cr alloy as well as the composition and microstructure of the resulting oxide scale were characterized by scanning electron microscope and x-ray diffractometer in the condition that the alloy was exposed to the 75%(mass fraction) Na2SO4 + 25%(mass fraction) NaCl mixed salt. Results showed that the Ti48Al2Nb2 Cr alloy in service corroded seriously in this mixed salt, and after an oxidation at 700 ℃ for 100 h, the net weight gain of the Ti48Al2Nb2 Cr alloy was-16.53 mg/cm2. The reason for the weight loss was the spalling of the oxide scale generated on the surface of the Ti48Al2Nb2 Cr alloy during the hot corrosion, as the oxide scale was loose and contained a high level of porosity so cannot firmly adhere to the substrate. The oxide scale could not prevent the in-diffusion of molten salt and oxygen or the out-diffusion of matrix elements. Moreover, the corrosion product NaNbO3 aggregated on the surface of the sample to form irregular block structures, which further destroyed the integrity of the oxide scale and resulted in a further deterioration of hot corrosion resistance.

Keywords

• ti48al2nb2cr alloy| mixed salt| hot corrosion behavior| mechanism;