Spray-based slurry spreading method for microscale laser powder bed fusion of copper

A spray-based slurry spreading method was developed for microscale laser powder bed fusion (μ-LPBF) of copper to address the challenges of submicron powder agglomeration and poor layer uniformity. In this method, submicron copper powders were dispersed in organic solvents with polymer-based dispersants to form a homogeneous slurry, which was then atomized and evenly deposited onto the substrate using an air spray gun. The electrostatic repulsion among long-chain polymer chains effectively reduced particle agglomeration, enabling uniform powder layer formation. Systematic experiments were conducted to investigate the effects of slurry composition and spray parameters, including atomization pressure, nozzle height, and flow rate, on the surface morphology, roughness, and layer thickness. The optimized parameters (atomization pressure 0.4 MPa, nozzle height 150 mm, flow rate 0.5 ml/s) yielded a smooth and uniform powder layer. Subsequent μ-LPBF experiments and thermo-fluid simulations revealed the mechanisms of melt pool evolution and defect formation, achieving continuous tracks and a surface roughness of 3.1 μm. This proposed method provides a simple and effective approach for uniform powder deposition in μ-LPBF and offers a promising route for high-precision microadditive manufacturing of copper.