Influence of solution temperature on microstructure and creep behaviors of a Ni–Co base superalloy for turbine disc

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2022-09, Vol.853, p.143741, Article 143741
• Main Authors: Zhou, Zijian, Zhang, Rui, Cui, Chuanyong, Zhou, Yizhou, Sun, Xiaofeng
• Format: Article
• Language: English
• Subjects: Carbide morphology; Carbides; Creep behavior; Creep life; Creep strength; Dislocations; Electron backscatter diffraction; Electron microscopy; Grain boundaries; Grain boundary character distribution; Microscopy; Microstructure; Morphology; Ni-Co base Superalloy; Nickel base alloys; Slip planes; Solution temperature; Stacking faults; Stress concentration; Superalloys; Turbine disks; Twin boundaries
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2022.143741

The influence of solution temperature on the microstructure evolution and creep behavior of a new Ni–Co base superalloy for turbine discs, including the grain morphology, grain boundary character distribution (GBCD), and grain boundary (GB) carbide morphology, was investigated using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The results showed that the creep fracture life first increased and then decreased with increasing solution temperature. The alloy solution treated at 1140 °C exhibited the best creep properties, with a creep life of 209 h. The enhanced creep performance of this alloy can be explained as follows: the volume fraction of GB carbides increased with increasing solution temperature, the diffuse fine granular carbides relieved stress concentration and strengthened GBs, the coarse primary γ′ phases rapidly dissolved, and the volume fraction of the fine and dispersed secondary and tertiary γʹ phases significantly increased. The narrower channels in the γ matrix increased the resistance to dislocation motion. The coherent Σ3 twin boundaries (TBs) with low interface energy hindered the dislocations and stacking faults intersecting the TBs on different slip planes. The relative frequency of Σ3 TBs increased to 53.6% when the solution temperature was increased to 1140 °C. The high proportion of Σ3 TBs played a key role in improving the creep resistance of the alloy. •Microstructure and creep behaviors were studied at different solution temperatures.•Creep life increased at first and thereafter decreased as solution temperature increased.•The continuous rod-like morphology of the M23C6 carbide degraded the creep properties.•The improved creep properties were determined by the increase of Σ3 TBs and fine γ′.