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.