Process driven self-organisation in laser powder bed fusion of copper coated diamond

Laser powder bed fusion (LPBF) of metal-diamond composites remains fundamentally limited by the extreme thermal gradients imposed by diamond. Here we demonstrate, for the first time, the LPBF of copper-coated diamond revealing previously inaccessible melt-pool behaviour. A narrow conduction-mode process window (150–220 J/mm 3 ) where single tracks exhibit <2.5% porosity and predictable geometric scaling was identified. Systematic single-track mapping reveals a unified thermo-fluidic response described by a vector regression model linking track geometry, porosity, particle assimilation and bonding to energy density. Multi-track experiments uncover six distinct morphological regimes, including a remarkable and previously unreported self-organised sub-micron porous lattice that emerges exclusively within a narrow 113–141 J/mm 3 window. This polygonal network (0.5–2 μm pores; 0.2–0.8 μm ligaments) forms through capillary-driven breakup of transient molten Cu films confined between overlapping tracks. By coupling classical van-der-Waals thin-film instability theory to LPBF specific melt-pool constraints, we derive the Robinson-Arjunan scaling law that predicts the lattice wavelength consistent with experimental observations. At higher energies, lattice coarsening, densification and keyhole-dominated porosity emerge. The results establish LPBF as not merely a consolidation route but a self-organisation platform for metal-diamond systems enabling engineered sub-micron architectures and tunable interfacial morphologies unattainable in monolithic metals. This work opens a new domain in additive manufacturing where feedstock design and melt-pool physics jointly govern hierarchical microstructure formation. • LPBF of copper-coated diamond demonstrated • Narrow conduction window yields micro/nano level porosity. • Self-organised sub-micron porous lattice • Thin-film instability drives polygonal lattice formation. • Robinson–Arjunan scaling law predicts lattice.