Role of W in W-coated Cu powder in enhancing the densification-conductivity synergy of laser powder bed fusion built Cu component

Abstract

Coating high laser-absorptivity alloying elements on Cu powder is effective in enhancing its compatibility with laser powder bed fusion (LPBF) but significantly sacrifices the electrical conductivity because of the distortion in the lattice structure of Cu matrix. To overcome this issue, high laser-absorptivity W nanoparticles with excellent stability were incorporated onto Cu powder through a novel powder coating approach. Experimental results indicated that W-coating significantly reduced the laser reflectivity of Cu powder, enabling the complete melting of powder. Minor addition of W-coating improved the relative density to greater than 98.5% even at a high scanning speed of 800 mm/s. During the LPBF process, the evolution of W started with sintering of partial W-coating nanoparticles and agglomerations prior to the melting of Cu powder. Subsequently, the remaining was submerged into the Cu melt because of the capillary forces. After solidification, W was finally present in two forms: agglomerations localized around the melt pool boundary and nanoparticles dispersed in the Cu matrix. No significant solid solution was detected in the solidified Cu matrix. Scanning speed played a key role in determining the sintering behavior of W-coating at the early stage of LPBF and can be employed to tune the proportion of agglomerations and nanoparticles. Under the optimized printing conditions, a near-fully dense Cu component with excellent electrical conductivity (96%IACS) was obtained by printing 0.5 vol% W-coated Cu powder, which was superior compared with the reported data of printed Cu components incorporating other laser-absorptivity enhancers.