Effect of Deposit Chemistry on the Stress Corrosion Cracking Susceptibility of CMSX-10 at 550°C and 700°C

Turbine blades of aerogas turbines can be at risk of stress corrosion cracking (SCC) below 700 °C due to the effects of stress, sulphur-containing gases and deposits that are ingested into the turbine. Therefore, understanding the effect of different deposits on the SCC susceptibility of single-crystal nickel-based superalloys at different temperatures is crucial. This study investigated the effect of NaCl, sea salt and 80/20 mol% Na₂SO₄/K₂SO₄ on the SCC susceptibility of CMSX-10 at 550 °C and 700 °C. The results suggest that chlorine-containing salts play an important role in accelerating stress corrosion cracking at 550 °C, where the formation of HCl leads to the breaking down of the oxide and exposing the base alloy to a sulphidation environment. At 700 °C stress corrosion cracking is accelerated by the mix of sulphates that lead to reduced melting points, where the 80/20 mol% Na₂SO₄/K₂SO₄ has shown the highest susceptibility to SCC.