Influence of thermal exposure on the creep properties of an aluminized Ni-based single crystal superalloy in different surface orientations

Abstract

The effect of thermal exposure on the creep properties of an aluminized Ni-based single crystal superalloy in different surface orientations has been studied in the present study. The specimens were coated by a pack aluminizing process conducted at 1000°C for 5h under an argon atmosphere. Long-term exposure was performed at 1100°C for 500h prior to the creep test. The creep properties were found to deteriorate after the long-term exposure as a result of the coarsening of γ′ precipitates accompanied by the formation of a secondary reaction zone which is known to degrade the strength of aluminide coating on a Ni-based single crystal superalloy. The formation of a topologically close-packed phase is one of the degradation factors that are responsible for the reduction of the creep strength of the aluminide coating on a Ni-base single crystal superalloy both with and without long-term exposure. The anisotropic creep properties between the two side-surfaces are due to the different arrangements of {111}〈101〉 slip systems.