On Pipe Diffusion of Rhenium along Misfit-Dislocation-Networks in Ni-base Single Crystal Superalloys

Abstract

This study explores whether the diffusion of Re in the γ-phase of Ni-base superalloy single crystals is accelerated along fine dislocation networks that have formed at γ/γʹ-interfaces during high-temperature and low-stress creep. Diffusion couples of Re-enriched superalloy thin films were sputter deposited onto (100) planes of two Re-free single-crystalline nickel-base superalloys with different microstructures. One consisted of an as-processed microstructure with cuboidal γʹ-particles separated by thin γ-channels, with a low dislocation density. The other featured continuous γʹ-rafts parallel to the [100] direction with fine dislocation networks at the γ/γʹ-interfaces. The rafted structure was produced by 2% creep deformation along the [001] direction at 1000°C and 240 MPa. Analytical transmission electron microscopy and atom probe tomography revealed that the diffusion of Re into the γ-phase was not accelerated by the presence of dislocation networks at the γ/γʹ-interfaces of the rafted microstructure.