High Temperature Stress Rupture Anisotropy of a Ni-Based Single Crystal Superalloy

Abstract

High temperature stress rupture anisotropies of a second generation Ni-base single crystal (SC) superalloy specimens with [001], [011] and [111] orientations under 900 °C/445 MPa and 1100 °C/100 MPa have been investigated in the present study, with attentions to the evolution of γ/γ′ microstructure observed by scanning electron microscopy and the dislocation configuration characterized by transmission electron microscopy in each oriented specimen. At 1100 °C/100 MPa as well as 900 °C/445 MPa, the single crystal superalloy exhibits obvious stress rupture anisotropic behavior. The [001] oriented specimen has the longest rupture lifetime at 900 °C/445 MPa, and the [111] oriented sample shows the best rupture strength at 1100 °C/100 MPa. While the [011] oriented specimen presents the worst rupture lifetime at each testing condition, its stress rupture property at 1100 °C/100 MPa is clearly improved, compared with 900 °C/445 MPa. The evident stress rupture anisotropy at 900 °C/445 MPa is mainly attributed to the distinctive movement way of dislocations in each oriented sample. Whereas, at 1100 °C/100 MPa, together with the individual dislocation configuration, the evolution of γ/γ′ microstructure in each orientation also plays a key role in the apparent stress rupture anisotropy.