Phase chemistry of the superalloy SC16 after creep deformation Original Research Article

The local chemical concentrations of the elements in the nickel-based single crystal superalloy SC16 were examined by atom probe field ion microscopy (APFIM) after standard heat treatment and after creep strain of 1.35% at 1223 K. The measurements were carried out along the [001] direction parallel to the applied creep stress. An enrichment of Al and a slight depletion of Ti in the γ′ precipitate near the γ′/γ interface were observed in both states, the as-prepared and the creep-deformed. The average chemical composition of the γ′ precipitates had hardly been changed during the creep deformation. However, the average Cr content decreased in γ channels perpendicular to the applied stress significantly. Its enrichment was detected near the interface. Contrary to Cr, the average Ni concentration increased in these γ channels and depleted near the interface. Both Ti and Ta seem to be depleted in γ channels near the interface after creep deformation. According to the results, the long range diffusion for directional coarsening of γ′ precipitates is suggested to take place mainly in γ channels.