Optimisation of Copper production by laser powder bed fusion (L-PBF)

Additive Manufacturing (AM) refers to a family of layer-upon-layer building technologies capable of producing geometrically intricate parts in a single step [1]. In the last twenty years it has gained huge interest in both academia and industry. Today, still, the processability of many materials through AM is under development. One of the most interesting study concerns the adoption of copper, a metal characterized by high thermal and electrical conductivity. The first part of this thesis presents a global review of the current state of art on copper’s manufacturing through AM. In the pages that follow the main studies conducted so far concerning this issue are reported. As a result, all the challenges that arise in copper processing and the solutions proposed to overcome them and realize high quality copper components are exposed. Further, in the present experimental activity, a new material solution is proposed in order to improve the processability of copper powder through Laser Powder Bed Fusion (LPBF). The idea is to add graphite to copper powder. As a matter of fact, graphite reduces thermal expansion and improves thermal conductivity of copper. Due to graphite’s higher laser absorption rate, the resultant mixture should be easier to manufacture through laser techniques. Thus, graphite can be one of the best candidates to improve significantly the processability of copper powder through Laser AM (LAM). At the same time the spread ability of the mixture can be negatively affected by the elevated lubricant property of graphite. In addition, if the quantity of graphite added is too much, Van der Waals forces will induce agglomerations. Finally, also the addition of a small quantity of an alloying element, would drastically decrease the electrical conductivity of copper [2]. Consequently, is fundamental to carefully choose the quantity of graphite to be added. So far, however, very little attention has been paid to the role of graphite added to copper powder. The central thesis of this experimental work is to study the effects of the addition of different amounts of graphite to copper powder and to define the processing parameters suitable to produce copper 3D printed components.