Turbine blades in aircraft engines may encounter overheating and suffer serious creep property degradation. In this study, the thermal cycling creep experiments were conducted on K465 superalloy under (900 °C/30 min–1100 °C/3 min)/50 MPa, (900 °C/30 min–1150 °C/3 min)/50 MPa and (1000 °C/30 min–1150 °C/3 min)/50 MPa. The investigated thermal cycling creep properties were dramatically degraded, and increasing the overheating temperatures significantly decreased the thermal cycling creep life. The secondary γ′ precipitates obviously dissolved and the area fraction decreased to around 35.2% under (900 °C/30 min–1150 °C/3 min)/50 MPa and (1000 °C/30 min–1150 °C/3 min)/50 MPa, which was almost half that after the standard solution treatment. The decline of the thermal cycling creep properties was mainly due to the significant dissolution of γ′ precipitates. The creep holes/cracks were mainly distributed at the M6C carbides and γ/γ′ eutectics interfaces, M6C carbides and γ′ film interfaces in the grain boundaries, and resulted in the final intergranular fracture.

Ni-based superalloys are widely used to manufacture gas turbine core components, but reports on the reliability of superalloys at cryogenic temperatures are still limited. Considering the actual application of superalloys in the field of cryogenic temperature, the tensile deformation behavior of directionally solidified superalloy DZ406 was investigated at cryogenic temperatures from −125 °C to 25 °C, and the comparative analysis of room temperature and 1000 °C was carried out. The yield strength and ultimate strength at cryogenic temperatures were close to that at room temperature, and twice that at 1000 °C. The elongation was maintained at 10–15% and exhibited a certain plasticity at cryogenic temperatures. The morphologies and chemical composition of γ′ precipitates were close at cryogenic temperatures, room temperature and 1000 °C. The microstructure difference that was caused by different temperatures was mainly reflected in the fracture mode and dislocation configuration. At cryogenic temperature, the fracture samples basically exhibited no necking phenomenon, and the cracks were basically located in the interdendritic regions and occurred in MC carbide itself; at room temperature and 1000 °C, dimples with carbides inside were distributed on the fracture surface. Slip bands and dislocations contributed to the tensile deformation at cryogenic temperatures and room temperature, while only the dislocations worked at 1000 °C.

No abstract