Effects of solution temperatures on creep resistance in a powder metallurgy nickel-based superalloy

In this study, FGH96 superalloys with different microstructures were prepared via solution heat-treatment at different temperatures. Herein, creep tests were conducted on the resulting FGH96 alloys at 704 degrees C and 690 MPa, and the creep properties and microstructures of the samples were found to have a complex relationship. To understand the deformation mechanism of FGH96 alloys, the gamma' distribution, grain boundary morphology (including small-angle boundaries, large-angle boundaries, and Sigma 3 twin boundaries), and local misorientation during creep were analyzed using scanning electron microscopy, transmission electron microscopy, and electron backscattered diffraction, respectively. The results suggest that the main creep deformation mechanism in FGH96 superalloys is microtwinning. Furthermore, we investigated the interaction between Sigma 3 twin boundaries and microtwins and found that the Sigma 3 twin boundaries had a positive effect on the creep resistance. Based on the analysis of kernel-averaged misorientation and Schmid factors of the deformed grains, we found that the higher dislocation density around the small-angle boundaries was the main reason for the greater creep rate in the subsolvus superalloy. The effects of serrated grain boundaries and weight percent of the carbide were also studied to investigate the damping of creep properties in samples that are treated at temperatures of 1180 degrees C or higher. The overall creep resistance was determined by the frequency and density of small-angle boundaries, large-angle boundaries, and Sigma 3 twin boundaries.

Automated summary

This study investigated the creep properties of FGH96 superalloys with different microstructures and found a complex relationship between creep properties and microstructures. The main creep deformation mechanism was identified as microtwinning, with Sigma 3 twin boundaries having a positive effect on creep resistance. The higher dislocation density around small-angle boundaries was found to be the main reason for increased creep rate in subsolvus superalloys.