Effect of heat treatment on the microstructure and properties of the GH3625 superalloy

The rupture property of the GH3625 alloys is significant for the long-term service of concentrated solar power (CSP) plants. This study focuses on the microstructural evolution of the homogenized and thermally exposed GH3625 alloy sheets during the stress rupture tests through fine characterizations. The γ″ phase precipitated after the thermal exposure at 595 °C/300h was discovered to optimize the rupture property, except for the tests under 595 °C/552 MPa and 595 °C/621 MPa, in which the deformation twins and SFs were observed in the homogenized alloys. Meanwhile, the γ″ phase was also discovered to precipitate along the slip bands in the long-term tested alloy (595 °C/552 MPa). The deformation twins and SFs were not observed in the thermally exposed alloys, while they exist in the homogenized alloys after rupture to fracture. The deformation twins become thinner with rising testing temperature from 595 to 705 °C under 552 MPa. The γ″ phase, deformation twins, and SFs were confirmed to be in favor of elevating the rupture property of the GH3625 alloy. This study provides fundamental data for the long-term stability of GH3625 superalloy in CSP, while establishing a robust theoretical foundation for the subsequent optimization of the alloy's performance.