Hot corrosion behavior of powder metallurgy Rene95 nickel-based superalloy in molten NaCl–Na2SO4 salts

Hot corrosion behavior of powder metallurgy (PM) Rene95 Ni-based superalloy in molten 25%NaCl + 75%Na2SO4 salts at 650 °C, 700 °C and 750 °C are investigated by weight loss measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Experimental results show that hot corrosion kinetics follow a square power law at 650 °C and linear power laws at 700 °C and 750 °C. The corrosion layers on the surface of PM Rene95 superalloy are detected to be mainly composed of Cr2O3, NiO, and Ni3S2 at each temperature. Besides, small amounts of NiCr2O4 at 700 °C and NaCl at 750 °C are observed respectively. Cross-sectional morphologies and corresponding elemental maps indicate that corrosion layers near scale/alloy interface are composed of oxides at 650 °C while duplex oxides and sulfides at 700 °C and 750 °C. According to these results, a cooperating mechanism of oxidation and sulfuration for hot corrosion of PM Rene95 Ni-based superalloy is confirmed.