Effect of long-term aging treatment on the tensile strength and ductility of GH 605 superalloy

Aging treatment is an effective way to optimize the mechanical properties of Co-based superalloys. In this study, commercial GH 605 superalloy was subjected to aging treatment at 650 ​°C in a wide time range up to 1000 ​h. The effects of aging time on the tensile characteristics, microstructure evolution and mechanical properties were systematically investigated at room temperature (RT) and 900 ​°C. The results showed that the volume fractions of M₆C and M₂₃C₆ carbide increased with the aging time. After long-term aging treatment, the yield strength (YS) at RT was enhanced from 490.3 ​MPa to 805.9 ​MPa, while the alloy still had high tensile ductility (above 20%). Microscopic observations by transmission electron microscopy (TEM) indicated that the strengthening mechanism was related to carbide precipitation inside the grains and the change in the dislocation slipping mode. Moreover, long-term aging treatment can increase the elongation from 24.1% to 47.3% at 900 ​°C accompanied by a slight increase of YS from 299.3 ​MPa to 313.9 ​MPa. Based on detailed microstructure analysis the strengthening mechanism can be attributed to the refined grains as well as carbide precipitation inside the grains and around the grain boundaries.