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 mu m. 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 cm(3)/h.