Coarsening behavior of γ″ precipitates in GH4169 superalloy fabricated by laser solid forming

The bulk of GH4169 superalloy was fabricated by laser solid forming (LSF). The bulk sample was treated with two-step aging treatment at 720-780℃ for different holding times. The morphology, size and coarsening kinetics of γ″ precipitates of LSFed GH4169 superalloy were studied by microscopic measurements. The results show that the γ″ precipitates evolve gradually to be disc-shaped in morphology during two-step aging treatment with different holding time. Compared with the holding time, the aging temperature has more significant effect on the γ″ precipitates. Meanwhile, the coarsening behavior of the γ″ precipitates obeys the Lifshitz-Slyozov-Wagner(LSW) theory. The diffusion activation energy Q in coarsening of γ″ precipitates precipitated in the LSFed GH4169 superalloy is 281.85 kJ/mol. It is slightly higher than that of the forged GH4169 superalloy, which indicates that the structural stability of LSFed GH4169 superalloy is better than that of the forged one.