Anisotropic stress rupture properties of the nickel-base single crystal superalloy SRR99

摘要

The influence of orientation on the stress rupture properties of a single crystal superalloy SRR99 was investigated at temperatures of 760 and 1040℃. It is found that the creep anisotropic behaviour is pronounced at the lower temperature of 760 ℃ and the stress rupture life ranks in the order [0 01 ] > [111 ] > [011 ]. Despite the anisotropy of stress rupture life is evidently reduced at the higher temperature, the [111] orientation exhibits the longest life. At 760℃, EBSD (electron back scattered diffraction) was adopted to measure the lattice rotation and the deduced results indicate that the dominant slip systems are (11 2) {111} during stress rupture test. At 1040 ℃, the ranking order of the stress rupture lifeis[111]>[001]>[011] and the single crystal close to [011 ] orientation still shows the poorest life. In the [001] and [1 11] samples, regular γ' raft structure is formed compared with [011]samples. Further observations made by TEM investigations reveal the underlying deformation mechanisms for crystals with orientations near [0 01 ], [011 ] and [111] under two test conditions.