Effect of Annealing on Microstructure and Tensile Properties of Selective Laser Melting MAR-M509 Superalloy

To solve the anisotropy problem of selective laser melting (SLM) MAR-M509 superalloy, the effect of annealing on microstructure and tensile properties of SLM-deposited MAR-M509 samples was investigated. Annealing temperature was derived by JMatPro simulation. Microstructure, tensile properties, and microhardness of the as-deposited and annealed samples were studied. Results showed that most of the grains in the as-deposited samples were columnar crystals growing along the <001> crystal direction, and the microstructure was composed of γ matrix and MC carbide. After annealed at 1160 °C for 4 h with water cooled, most of the columnar grains transformed into near equiaxed grains; microstructure was composed of γ, M₂₃C₆, Cr₇C₃, and MC. Micron-scale carbides and nanoscale carbides were dispersed in grain boundaries and within grains, respectively. The tensile properties in the horizontal and vertical directions became very close. The tensile fracture mechanism of both as-deposited and annealed specimens was intergranular ductile fracture.