Effect of rhenium addition on isothermal oxidation behavior of single-crystal Ni-based superalloy

The isothermal oxidation behavior of a nickel-based superalloy, which we designate as DD32, containing 4 wt.% rhenium and another alloy (DD32M) without rhenium were investigated at 900, 1000 and 1100 degrees C. Oxidized alloys were characterized by SEM, EDX, EPMA and XRD. The two alloys revealed similar oxidation rates at 900 degrees C, while the DD32 alloy showed a slightly higher mass gain than that of the DD32M alloy during 1000 and 1100 degrees C exposure. Surface and cross-sectional examination indicated that DD32 alloy showed nonuniform oxidation between dendritic and interdendritic areas at all temperatures. Similar different oxidation behavior between dendritic and interdendritic regions was also observed in the DD32M alloy at 900 degrees C. However, DD32M showed relatively uniform oxidation at 1000 and 1100 degrees C exposure. Therefore, Re addition clearly induced the nonuniform oxidation of the alloy. (c) 2005 Elsevier B.V. All rights reserved.