Synergistic effect of multiple molten salts on hot corrosion behaviour of Ni-based single crystal superalloy

Hot corrosion behaviour of Ni-base single crystal at 900℃ is investigated under three different mixed salts. The result shows that hot corrosion degree in Na 2 SO 4 +NaCl+NaVO 3 is the most serious, followed by Na 2 SO 4 + NaVO 3 , and Na 2 SO 4 +NaCl is the least. The hot corrosion mechanism of superalloy in Na 2 SO 4 +NaCl+NaVO 3 salts is proposed. More importantly, the interaction of Na 2 SO 4 , NaCl and NaVO 3 is a synergistic relationship in which Na 2 SO 4 causes a basic corrosion attack, and NaCl with NaVO 3 strengthen this attack. Therefore, in hot corrosion protection, the type of corrosive salt should be reduced to avoid the synergistic effect caused by multiple salts. • Hot corrosion behavior of Ni-based single crystal superalloys at 900℃ under three different mixed salts was investigated. • During hot corrosion process, sulfides in γ′-depleted layer are mainly affected by the critical oxygen partial pressure and standard free energy of sulfide. • NaCl and NaVO 3 consume the protective oxides and prolong the time of internal sulfidation-oxidation cycle reaction. • Between the corrosion salts of Na 2 SO 4 , NaCl and NaVO 3 , there is a synergistic relationship, where Na 2 SO 4 causes a basic corrosion attack and NaCl with NaVO 3 strengthen this attack.