Influence of the Impurity Element Sb on Oxidation Resistance and Creep Strength of the Ni-Base Single Crystal Superalloy TMS-238

Abstract

The influence of impurity element Sb on the oxidation resistance and creep strength of the single crystal superalloy TMS-238 was studied in this work. It was found that 1.1 ppm Sb clearly degrades the oxidation resistance, but not for the creep strength. As we increased the amount of Sb up to 3.8 ppm, the weight loss of the sample increased, as expected for the effect of Sb on the oxidation resistance. To understand the mechanism, the oxide structure was characterized by scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDS), and three-dimensional atom probe (3DAP) was used to visualize the Sb distribution. 3DAP analysis has revealed Sb segregation of 0.03 at% to 0.04 at% at the oxide/substrate interfaces for 3.8 ppm Sb sample. These results indicated that the segregation of Sb, a low melting point metallic impurity, at the oxide/substrate interface degrades the oxidation resistance for TMS-238.