Enhancing mechanical properties and suppressing intermediate temperature embrittlement of Hastelloy X by nano-TiC additions using laser directed energy deposition

High-density Hastelloy X (HX) samples and nano-TiC reinforced HX composites with varying TiC contents (1 wt.%, 2 wt.%, and 4 wt.%) are fabricated using laser directed energy deposition (LDED). The effects of nano-TiC addition on microstructure and tensile properties at 25 °C and 850 °C are systematically investigated. The results show that the nano-TiC reinforced composites exhibit superior mechanical properties compared with wrought HX. At 25 °C, the composite containing 2 wt.% nano-TiC achieves a yield strength (YS) of 442 MPa and an ultimate tensile strength (UTS) of 807 MPa, representing 36 % and 12 % improvements over wrought HX, respectively, while maintaining a comparable elongation. At 850 °C, the composite achieve a strength of 317 MPa, with elongations exceeding 52%, significantly higher than that of pure HX (14%) and comparable to wrought HX (51%). Microstructural analysis reveals that nano-TiC addition refines the grain structure, modifies the morphology and distribution of carbides, and suppresses elemental segregation. These microstructural refinements collectively enhance the composites’ strength, and quantitative analysis further indicates that solid solution strengthening and dislocation hardening are the primary contributors to yield strength. The incorporation of nano-TiC effectively mitigates the intermediate temperature embrittlement of pure HX by eliminating the chain-like grain boundary carbides and continuous interdendritic carbides, and forms ∼1 μm carbides within grains. These findings offer valuable insights into strengthening and embrittlement suppression mechanisms in particle reinforced Ni-based superalloys fabricated via additive manufacturing. • Elucidation of microstructural formation mechanism in LDED HX and nano-TiC composites. • Enhanced tensile properties at room and intermediate temperatures beyond wrought HX. • Quantitative assessment of solid-solution and dislocation strengthening induced by nano-TiC. • Suppression of intermediate temperature brittleness through nano-TiC addition.