Understanding of microstructure and mechanical properties of heat-treated Ti3SiC2/Inconel 625 matrix composites manufactured by laser-directed energy deposition

To enhance the metal components by laser-directed energy deposition (LDED), adding reinforcement particles and exerting post treatments are widely identified as the two effective methods. However, how post heat treatments influence the performance of precipitated particle reinforced metal composites acquired by laser additive manufacturing (AM) processes has rarely been investigated. In this work, Inconel 625 matrix composite reinforced by Ti 3 SiC 2 particles was manufactured using LDED. The microstructure and mechanical property of LDED-produced composite were experimentally investigated under three heat treatments including solid solution treatment (SST), aging treatment (AT) and solid solution plus aging treatment (SSAT). The results showed that after solid solution treatment at 1150 °C for 2 h, the Laves phase and carbide redissolved, and recrystallization took place within the material, thus improving the plasticity of the composites. After aging treatment at 700 °C for 24 h, a large number of carbide phases precipitated in the composite material, subsequently resulting in greatly improving the hardness and tensile strength and reducing the elongation. However, solid–solid phase transition occurred during the aging process at 800 °C, and a large number of acicular δ phases were precipitated between the dendritic arms, which led to a reduction in the strength and plasticity of the composite. After solid solution plus aging treatment, the comprehensive mechanical properties of Ti 3 SiC 2 /IN625 composites were significantly improved. The improvement of comprehensive mechanical properties in Ti 3 SiC 2 /Inconel 625 composite was the co-strengthening results of dispersed particles in the crystals and massive and granular carbides that precipitated at grain boundaries.