Effects of Solution Treatment Temperature on Microstructures and Properties of Laser Solid Forming GH4169 Superalloy

The effects of the solution treatment temperature on the microstructure, the chemical composition homogeneity and the microhardness of laser solid forming GH4169 superalloy were investigated. It is found that the grain boundaries become clearer with increasing of the solution treatment temperature. The recrystallization occurs when the samples are solution treated at 1000–1170 °C for 1 h; when the solution treatment temperature is higher than 1000 °C, a large number of twin crystals can be observed, and the grains are refined remarkably compared with the as-deposited grains. The chemical homogeneity can be achieved through solution treatment at 1100 °C for 1 h. With increasing of the solution treatment temperature, the microhardness first decreases rapidly, and then slowly when the solution treatment temperature is above 1100 °C. The variation of microhardness can be explained based on the precipitation behaviors of γ′, γ″ and δ phases during the solution treatment. It is concluded that the temperature of 1100 °C is the low limit of solution treatment temperature range for laser solid forming GH4169 superalloy.