Influence of tungsten particle size on microstructure and mechanical properties of high strength and tough tungsten particle-reinforced nickel-based composites by laser-direct energy deposition

Tungsten (W) particle-reinforced nickel (Ni)-based composites were fabricated via laser-direct energy deposition (L-DED). The influence of the W particle size on the microstructure and mechanical properties of the deposited samples was systematically studied. The results indicate that refining the W particle size could refine the γ-Ni grains and subgrains, thin the (Ni, Cr)4 W interface layer, and increase the dislocation density of the intergranular matrix, thus improving the tensile strength and elongation of the L-DED samples. As W particle size decreased from 75 to 150 μm to 6.5–12 μm, the tensile strength and elongation of the deposited samples increased by 150 MPa and 2.9 times to 1347.6 ± 15.7 MPa and 17.5 ± 0.4%, respectively. Based on the properties of the interface (Ni, Cr)4 W, a load-transfer efficiency factor suitable for this composite was proposed and the load-transfer strengthening formula was optimized. A quantitative analysis of the strengthening mechanisms was established considering load-transfer strengthening, Hall–Petch strengthening, thermal-mismatch strengthening, and solid-solution strengthening. The calculated contribution of each strengthening mechanism to the yield strength and theoretical calculations were in good agreement with the experimental data. The article breaks the bottleneck of poor plasticity of W particle-reinforced Ni-based composites prepared by L-DED and provides a theoretical basis for the construction design of W particle-reinforced Ni-based composites with excellent mechanical properties.