Hot corrosion behaviors of a Cr 13Ni 5Si 2-based metal silicide alloy in Na 2SO 4 + 25 wt.% K 2SO 4 and Na 2SO 4 + 25 wt.% NaCl molten salts

Abstract

Hot corrosion behaviors of a near single-phase Cr 13Ni 5Si 2-based ternary metal silicide alloy in molten Na 2SO 4 + 25 wt.% K 2SO 4 at 900 °C and Na 2SO 4 + 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 Na 2SO 4 + 25 wt.% K 2SO 4 due to the very high Cr content, promoting the formation of a continuous and protective Cr 2O 3 oxide layer which acted as effective barriers to the inward diffusion of corrosive species during the hot corrosion process. Addition of NaCl to Na 2SO 4 accelerated the cracking and spalling of the Cr 2O 3 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 Cr 13Ni 5Si 2-based metal silicide alloy in Na 2SO 4 + NaCl salts was much more severe than in Na 2SO 4 + K 2SO 4 salts.