Laser powder bed fusion of a tungsten-nickel-ferrum alloy via in-situ alloying: Densification, microstructure, and mechanical properties

This work investigated the fabrication of a 50W–35Ni–15Fe alloy in situ via laser powder bed fusion (LPBF) using the mixed powders of 50 wt% W, 35 wt% Ni, and 15 wt% Fe. The influence of the laser energy density on the densification, surface morphology, microstructure and mechanical properties of the LPBF-printed 50W–35Ni–15Fe alloy was investigated. An increase in the laser energy density (148‐250 J/mm3) can result in an improvement in the relative density, and the highest relative density of 99.3% can be obtained at 250 J/mm3. The microstructure of the 50W–35Ni–15Fe alloy consists of a γ(W, Ni, Fe) matrix and W particles dispersed in the matrix. During the LPBF process, the W powder undergoes the process of melting and dissolution in melt pools. The coalescence of melted/dissolved W powder leads to the large-sized W particles, while the nanosized W particles are precipitated in the matrix. Cellular grains of γ are formed around the retained W particles and grow along the thermal gradient to form columnar grains. The 50W–35Ni–15Fe alloy printed under the laser energy density of 250 J/mm3 exhibits the highest ultimate tensile strength of 732.17 MPa and elongation of 5.64%. The mechanical strengths were attributed to the synergistic effect of solid solution strengthening and dispersion strengthening. The findings can provide the reference for the development of in situ alloying of W-based alloys by LPBF.