Microstructural homogenization and high-temperature cyclic oxidation behavior of a Ni-based superalloy with high-Cr content

A new Ni-based superalloy with high-Cr content was designed for industrial gas turbines application. The microstructural homogenization and high-temperature cyclic oxidation behavior was investigated systematically. The results showed that the optimum heat treatment condition was 1563 K (1290 °C)/4 h + 1573 K (1300 °C)/6 h, A.C. (air cooling) + 1393 K (1120 °C)/2 h, A.C. + 1143 K (870 °C)/24 h, A.C., which can completely dissolve the γ/γ′ eutectic and the Ni₃(TiTa) phase in the interdendritic region. The cyclic oxidation results showed that a multilayer of continuous and dense oxide-rich regions formed and the kinetic curves followed a parabolic law. The mass gain at 1323 K (1050 °C) and 1343 K (1070 °C) was 4.02 mg/cm² and 4.23 mg/cm², respectively. No severe spallation of the oxide-rich region was observed. The outer layer of the oxide-rich region mainly consisted of Cr₂O₃, TiO₂, and (Ni, Co)Cr₂O₄ spinels, while the layer at the substrate-oxide interface was found to be Al₂O₃. The results show that this new superalloy has a better cyclic oxidation resistance at 1343 K (1070 °C) than the commonly used IN738 and GTD-111 superalloys.