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Abstract. The microstructure evolution and stress rupture properties at 1100℃/140MPa of a Ru-containing single crystal superalloy after long term aging at 1100℃ for 200h-1000h were investigated. The results showed that the γ′ phase rafting and the γ matrix channel broadening appeared after long term aging. The rafting degree enhanced with increasing of aging time. A small amount of TCP phase began to appear after aging for 200h. The volume fraction of TCP phase after aging for 1000h was only 0.1%, which indicated the alloy had excellent microstructure stability. The stress rupture life of the alloy at 1100℃/140MPa represented the decrease tendency with increasing of aging time. The γ′ rafting and TCP phase precipitation were the main factor for this degradation.Keywords: single crystal superalloy; long term aging; microstructure stability IntroductionIn recent years, nickel based single crystal superalloys are key materials for the production of turbine blades in modern aerospace engines [1, 2]. The temperature capability of the single crystal superalloys has greatly improved over the past few decades. Significant progress has been gained by raising the content of refractory elements [3][4][5]. These refractory elements, such as Re and W, can enhance the creep properties of single crystal superalloys. However, deleterious topologically close packed (TCP) phase are often appeared in the single crystal superalloys with high fraction refractory elements. The mechanical properties at high temperature can decrease because of TCP phase precipitation [6,7]. So microstructure stability is a focus problem in the design process of next generation single crystal superalloy [8][9][10]. This paper examines the effect of long term aging on the microstructure and stress rupture properties of the new generation single crystal superalloy. The microstructure development and TCP phase formation during long term aging were investigated. The purpose of this study is to improve the application of a new generation single crystal superalloy.