Limits and solutions in processing pure Cu via selective laser melting using a high-power single-mode fiber laser

The demand for additive manufacturing (AM) of Cu and its alloys shows an increased trend from the energy and heat transfer–related applications. Selective laser melting (SLM) is amongst the key AM processes for metals, providing high geometrical accuracy and design flexibility. The technology is most commonly employed using high-brilliance fibre lasers operating at 1 μm. However, the elevated reflectivity of Cu at this wavelength, combined with its high thermal conductivity, is the cause for a highly unstable process, whereby pore-free products are difficult to obtain. Accordingly, the present work explores the limitations in processing pure Cu powders with a 1-kW single-mode fibre laser providing solutions and different strategies for improving part quality. The process parameters were studied for single and multi-pass melting strategies. The power level requirements, as well as the build plate material, are assessed through an analytical model. The results demonstrate that a correct sequence of multi-pass strategies can improve the part density up to 99.1% ± 0.2% with an industrially acceptable build rate of 12.6 cm3/h.