Evolution of microstructures and properties of the GH4169 superalloy during short-term and high-temperature processing

The effects of short-term (less than 1 h) and high-temperature processing (850–1050 °C) in the temperature range between the commonly used aging temperature and solution temperature on the microstructure, mechanical properties, and corrosion resistance of the GH4169 superalloy is investigated systematically. With increasing temperature and time, strengthening precipitates such as the γ′ and γ″ phases in the grains and carbides in the grain boundaries dissolve in the matrix gradually consequently decreasing the tensile strength and yield strength and increasing the ductility. Evolution of the precipitates with temperature is consistent with thermodynamic calculation and grain growth is associated with evolution of the precipitates during the short-term and high-temperature processes. The grains grow slowly and the activation energy is less than 45.4 KJ/mol when the temperature is below 1000 °C. However, as the temperature is increased from 1000 °C to 1050 °C, the grains grow rapidly and the activation energy is about 398.5 KJ/mol. The GH4169 superalloy treated at 900 °C for 10 min possesses superior mechanical properties including high strength and ductility. Electrochemical tests indicate that the corrosion resistance is improved by increasing the temperature. After the treatment at 1050 °C for 60 min, the self-corrosion potential E_corr and corrosion current density I_corr are −705.9 mV and 2.96 μA cm⁻², respectively, reflecting an increase of 177 mV and decrease of 22 μA cm⁻² compared to the untreated sample. There is evidence that the content in the precipitates plays a crucial role in the corrosion behavior of the superalloy and our results reveal many potential engineering applications for the GH4169 superalloy.