Study on W/Ni interface reaction and strengthening mechanism of tungsten particle reinforced nickel-based alloys by laser-direct energy deposition

Tungsten (W) particle reinforced nickel-based alloys were fabricated via laser-direct energy deposition, micro-structure and mechanical properties of the deposited samples were studied systematically. Results indicated that the deposited samples were composed of W particles, gamma-Ni matrix, interfacial reaction phase (Ni, Cr)4W and Laves phase. The W particles and the (Ni, Cr)4W, the (Ni, Cr)4W and the gamma-Ni matrix are both semi-coherent relations, which endows the W particles/gamma-Ni matrix interface high binding strength. The strong interface enables stress -strain transferred effectively between the W particles and gamma-Ni matrix during loading, and the particle rein-forcing effect was achieved. In addition, the W atoms dissolved in the laser molten pool played a solid solution strengthening role for the gamma-Ni matrix, which improved its tensile strength finally. Owing to the synergy effect of particle reinforcing and solid solution strengthening, the optimal ultimate tensile strength and elongation of the deposited sample was 1379.5 +/- 13.9 MPa and 8.1 +/- 0.9%, respectively. Fracture mechanisms of the deposited samples were investigated by in-situ tensile test, and cracks were observed initiation and propagation inside the W particles with the increase of tensile loads.

Automated summary

Tungsten particle reinforced nickel-based alloys were fabricated using laser-direct energy deposition, and the microstructure and mechanical properties of the deposited samples were investigated. The results showed that the samples consisted of tungsten particles, a gamma-nickel matrix, interfacial reaction phases, and Laves phases. The coherent relations between the tungsten particles and interfacial phases, as well as the interfacial phases and the gamma-nickel matrix, contributed to the high binding strength at the interface. The dissolution of tungsten atoms in the laser molten pool improved the tensile strength of the gamma-nickel matrix through solid solution strengthening. The synergy effect of particle reinforcement and solid solution strengthening resulted in the optimal ultimate tensile strength and elongation of the deposited sample.