Effect of Solid Solution and Aging Treatment on Microstructure and Hardness of Selective Laser Melting GTD222 Nickel-Based Alloy

The GTD222 nickel-based alloy was prepared by selective laser melting technique and then treated by solution at 1 150 ℃ and aging. The effects of solution treatment time (0,20,40,60,120 min), aging temperature (760,780,800,820,840 ℃) and aging time (2,4,8 h) on the microstructure and hardness of the alloy were studied. The results show that the columnar crystals in the GTD222 alloy formed by selective laser melting had a certain oblique angle to the forming direction. There were cellular substructures and high-density dislocations in the alloy, no γ' phase was precipitated, and MC carbides mainly distributed at grain boundaries and interfaces of adjacent substructures. The substructures of the alloy disappeared after solution treatment at 1 150 ℃. With increasing solution time, the carbides gradually dissolved, and the alloy hardness decreased first and then became stable. After aging at 760-840 ℃ for 2-8 h, a large number of γ' phases were precipitated in the alloy matrix. The size of γ' phase increased with aging time and temperature, while the hardness of alloy increased with increasing aging time and decreasing aging temperature.