Low Temperature Hot Corrosion Screening of Single Crystal Superalloys.

Single crystal superalloys were screened in Type II molten (Na,K)-sulfate hot corrosion re-coat tests in air +300 ppm SO₂ at 700 °C. They exhibited large 20⁻40 mg/cm² weight changes, repeated spallation, and non-protective, 25⁻50 μm thick corrosion layers after 300 h of testing. Scale cross sections revealed dual outer Ni(Co)O and inner Al(Cr)S-rich corrosion layers.