Hot corrosion behaviors of a Cr13Ni5Si2-based metal silicide alloy in Na2SO4 + 25 wt.% K2SO4 and Na2SO4 + 25 wt.% NaCl molten salts

Hot corrosion behaviors of a near single-phase Cr13Ni5Si2-based ternary metal silicide alloy in molten Na2SO4 + 25 wt.% K2SO4 at 900 °C and Na2SO4 + 25 wt.% NaCl at 850 °C were investigated respectively by weight change kinetics, surface and cross-sectional morphologies as well as X-ray analyses. Results indicated that the metal silicide alloy exhibited high hot corrosion resistance in molten Na2SO4 + 25 wt.% K2SO4 due to the very high Cr content, promoting the formation of a continuous and protective Cr2O3 oxide layer which acted as effective barriers to the inward diffusion of corrosive species during the hot corrosion process. Addition of NaCl to Na2SO4 accelerated the cracking and spalling of the Cr2O3 oxide scales and promoted the formation of sulfides in the alloy substrate beneath the oxide scales, leading to the propagation of hot corrosion. Therefore, the hot corrosion of the Cr13Ni5Si2-based metal silicide alloy in Na2SO4 + NaCl salts was much more severe than in Na2SO4 + K2SO4 salts.