Chlorine-induced Stress Corrosion Cracking of Single Crystal Superalloys at 550°C

Abstract This study has investigated the effect of NaCl and different gaseous environments on the stress corrosion cracking susceptibility of CMSX-4 at 550°C. The presence of SOx leads to the rapid dissociation of NaCl into Na₂SO₄ and the release Cl₂ and HCl, which then trigger an active oxidation mechanism and stress corrosion cracking. The incubation time for crack initiation at 690 MPa and in the presence of a sulphur containing environment is 10 minutes. A working hypothesis is that stress corrosion cracking occurs due to the hydrogen released at the oxide/alloy interface when metal chlorides are formed; however, this hypothesis needs to be further explored.