Hot Corrosion Behavior of Co–Al–W Superalloys with Si Additions

Abstract

The hot corrosion behavior of Co-9Al-9.5W-xSi (where x = 0%, 0.1%, 0.5%, at.%) alloys in a salt mixture at 900 °C was investigated. The effect of Si on hot corrosion resistance was examined using corrosion kinetics. The surface morphology of the corrosion products was explored via SEM with EDS and the phase constituents were examined using XRD. The results revealed that hot corrosion occurred as a combination of both sulfidation and oxidation behavior. With the increase in Si content, the hot corrosion resistance of the alloy was capable of remarkable advancement. Corrosion scales on the three Co-based alloys were mostly comprised of Co3O4, CoO, CoAl2O4, CoWO4, and Al2O3. The hot corrosion mechanism for the Co-based alloy in the presence of 75 wt.% Na2SO4 and 25 wt.% NaCl deposits were analyzed.