Microstructure and creep behavior of A 9%W single crystal nickel-based superalloy

Abstract

By means of the measurement of creep curves and microstructure observation, an investigation has been made into the microstructure evolution and creep behaviors of 9%W single crystal nickel-base superalloy. Results show that the alloy displays an obvious sensibility on the applied stress when applied stress is more than 160 MPa at 1040 °C. In the ranges of the applied temperatures and stresses, the apparent creep activation energy is measured to be about 465 kJ/mol. In the initial stage of creep, the cubical γ′ phase in the alloy is transformed into the N-type rafted structure along the direction vertical to the applied stress axis, the deformed mechanism of the alloy during steady state creep is dislocations climbing over the rafted γ′ phase, the dislocation shearing into the rafted γ′ phase is thought to be the creep mechanism of the alloy during later stage of creep. After crept up to fracture, the various morphology of the rafted γ′ phase is displayed in the different regions of the sample, the rafted γ′ phase vertical to the stress axis displays in the region far from the fracture, but the coarser twisted γ′ phase is detected in the regions near the fracture, which is attributed to the bigger plastic deformation occurred in the region near the fracture.