Effect of Long-term Thermal Exposure on Microstructure and Stress Rupture Properties of GH3535 Superalloy

The evolution of microstructure and the stress rupture properties of long term thermally exposed GH3535 alloy have been investigated. It was found that M6C carbides presented in the solid solution heat treated samples. During long term thermal exposure at 700 °C, fine M12C carbides precipitated preferentially at grain boundaries. These carbides coexisted with the pre-exiting M6C. The stress rupture life of 700 °C/1000 h exposed sample under creep testing at 650 °C/324 MPa is 93 h. It is much longer than that of the solid solution samples. No noticeable changes could be detected in both the microstructure and stress rupture lives when the samples were exposed for time longer than 1000 h M12C carbides were found to be beneficial to the creep properties. The cracks initiated at the interface of M6C carbides and matrix, which led to a lower creep rupture life.