Hot Corrosion Behaviour by Na₂SO₄ Deposits of the 1st Generation AM1 Single-Crystal Nickel-Based Superalloy at 750 °C

This paper highlights that hot corrosion at 750 °C can develop on the surface of AM1 nickel-based single-crystal superalloy (SX) turbine blades, whether in the As-Cast (AC) or Fully Heat-Treated (FHT) states even in the absence of SO₃ (g) flow. It was found that the 1 and 3 mg/cm² Na₂SO₄ deposits induce sulphidation, oxidation and basic flux at such low temperature like in Type I hot corrosion. Sulphidation is mainly located in the γˈ-depleted zone irrespective the substrate (AC and FHT). The metallurgical segregations in the AC superalloy extend the incubation period in contrast to what is observed upon pure oxidation. The increase in salt content showed a reduction in hot corrosive attack by forming a barrier layer.