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

Abstract

Tungsten (W) particle reinforced nickel-based alloys were fabricated via laser-direct energy deposition, microstructure and mechanical properties of the deposited samples were studied systematically. Results indicated that the deposited samples were composed of W particles, γ-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 γ-Ni matrix are both semi-coherent relations, which endows the W particles/γ-Ni matrix interface high binding strength. The strong interface enables stress-strain transferred effectively between the W particles and γ-Ni matrix during loading, and the particle reinforcing effect was achieved. In addition, the W atoms dissolved in the laser molten pool played a solid solution strengthening role for the γ-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.