The effect of crystallographic orientation on the oxidation behavior of a single-crystal nickel-base superalloy

The oxidation kinetics of DD100 nickel- base single- crystal alloy, with ( 221) and ( 100) surface orientations were tested in this study by thermogravimetry. A pronounced anisotropy in both the cyclic and isothermal oxidation resistance of DD100 alloy was observed. The ( 221) crystallographic surface of DD100 had a slower oxidation rate than the ( 100) surface when isothermally exposed to stationary air at 950degreesC, whereas the opposite results were obtained at 1050degreesC. When cyclically oxidized at 1100degreesC, the weight loss of samples with ( 221) surfaces was significantly greater than that of ( 100) surfaces, so that the cyclic- oxidation anisotropy was more remarkable at 1100degreesC than at 950degreesC. The different spatial alignment of the gamma' / gamma interface is thought to be responsible for the anisotropic oxidation behavior of the nickel- base single crystal alloy.