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

摘要

AbstractA 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/cm2and 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)Cr2O4spinels, 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.Highlights?A two-step solution treatment can fully homogenize the as-cast microstructure.?A multiple layer of continuous and dense oxide-rich region was formed during cyclic oxidation.?The oxidation resistance of this alloy was provided by a continuous and dense Cr2O3layer.?No severe spallation of the oxide layer of this polycrystalline superalloy was observed.]]>