Effect of Nb content on microstructure stability and stress rupture properties of single crystal superalloy containing Re and Ru

Abstract

Three experimental single crystal superalloys with 0%Nb, 0.5%Nb, 1.0%Nb were cast in the directionally solidified furnace, while other alloying element contents were basically kept unchanged. The effect of Nb on the microstructure, stability at 1100 °C and stress rupture properties at 1070 °C and 160 MPa of the single crystal superalloy were investigated. The experiment results show that the primary dendrite arm spacing decreases and the volume fraction of γ/γ′ eutectic of the alloy increases with the increase of Nb content in the as-cast microstructures. The size of γ′ phase particles becomes small and uniform and the cubic shape does not obviously change with the increase of Nb content. The precipitating rate and volume fraction of TCP phases increase significantly with the increase of Nb content in the process of long term aging at 1100 °C. The stress rupture lives increase and elongation decreases with increasing Nb content at 1070 °C/160 MPa. At last, the relationship between the microstructures stability, stress rupture properties of the alloy and Nb content is discussed based on JMatPro software and the lastest relevant database for single crystal superalloy.