Effects of Aluminum Addition on Microstructural Characteristics in Modified Coated Nickel-Based Superalloy, GTD-111, by Arc Melting

The nickel-based superalloys, grade GTD-111, were modified by aluminum addition by the mean of vacuum arc melting process, in order to improve microstructure and oxidation resistance at elevated temperatures. The arc melted GTD-111 specimens were added with aluminum of 1, 2 and 3 wt. %. All specimens were then performed with heat treatment, which consists of solution treatment for 6 h at various temperatures of 1125, 1145, 1165, 1185 and 1205°C. After that, all specimens were followed by precipitation aging at 845°C for 24 h. Finally, to evaluate the microstructural stability, the long-term heating at temperatures of 900 and 1000°C for 400 h were performed to the specimens. It was found that the most proper amount of aluminum addition was 1 wt.%, which provided reheat treated microstructures with high area fractions of γ′-precipitated particles, as well as uniformed distribution of cubic γ′-morphology. The most proper solutioning condition is also found at 1165°C for 6 h.