Effect of nano-TiC addition on microstructure and mechanical properties of Inconel 625 alloy fabricated by laser directed energy deposition

To enhance the mechanical properties of Inconel 625 alloy, this study incorporated nano-TiC particles at varying weight percentages (1 %, 2 %, 3 %, and 5 %) as reinforcements to fabricate metal matrix composites through Laser Directed Energy Deposition (DED). The microstructure evolution and mechanical properties were systematically investigated. The results indicate that the microstructure of the as-deposited Inconel 625 alloy was primarily dominated by columnar dendrites. With the increment of nano-TiC content, these dendrites were progressively refined, transitioning from a columnar to an equiaxed morphology. Moreover, the introduction of nano-TiC particles effectively reduced the space available for the growth of the Laves phase between dendrites. At a nano-TiC content of 5 %, the microhardness, yield strength, and tensile strength of the TiC/Inconel 625 composite were notably increased by 70 HV, 115.54 MPa, and 130.31 MPa, respectively. The tensile properties of the composites demonstrated higher strength but reduced ductility. The fracture surface analysis revealed typical dimple characteristics, indicating that the fracture mode was through microvoid coalescence. The comprehensive mechanical performance of the composite was optimized at a nano-TiC content of 3 %.