Tensile Deformation Behavior of a Directionally Solidified Superalloy at Cryogenic Temperatures

Abstract

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.