Laser additive manufacturing of a TiN strengthened nickel-based superalloy with tailored microstructure and tensile performance

Laser beam powder bed fusion (LB-PBF) technique shows unique advantage in fabricating the superalloy composites with distinct microstructure and enhanced mechanical properties. In this study, the LB-PBF method was first used to fabricate a novel Ni-Cr-W based superalloy composite doped with TiN particles (name as TiN/GH3230G composite). The effects of TiN addition on the metallurgical defects, microstructure characteristics and tensile properties of the LB-PBF TiN/GH3230G composite were systematically investigated. As the volume energy density (VED) increases, the relative density of the TiN/GH3230G composite increases first and then decreases. The formation of non-fusion pores and gas pores is the main reason for the poor forming quality at lower or higher VEDs. The highest relative density of 99.24 % can be obtained when VED is 83.33 J/mm³. However, compared with the LB-PBF GH3230G alloy prepared under the same parameters, some solidification cracks appear in the composite after the addition of TiN. The agglomeration of TiN particles, which can impede the liquid-phase feeding at the end of solidification process, is the main reason for the solidification cracking. The tensile properties results show that the addition of TiN can increase the yield strength both at room and high temperatures, owing to the Orowan strengthening and load-bearing strengthening induced by TiN particles. The agglomeration of TiN and the weak binding of TiN to matrix lead to the severe ductility reduction of the TiN/GH3230G composite.