The effect of functionalized graphene coated copper powder in laser powder bed fusion
Simon Tidén1, Mamoun Taher2, L.C. Diaz 2, Ulf Jansson1
1Uppsala University, 2Graphmatech AB
Graphene-metal composites are of high interest in additive manufacturing due to the possibility of both enhancing the processability of the powders and the properties of the printed parts. Printing high reflectivity materials, such as pure Cu for the common laser wavelengths, in laser powder bed fusion can be a challenge because only a small part of the input energy is absorbed by the material. In this ongoing study we have coated Cu powder with functionalized graphene sheets which reduced the reflectance of the powders with up to 67 % at 1060 nm. The reflectance of the Cu powder decreased as the graphene content was increased from 0 to 1.5 wt%. The decreased reflectance resulted in improved densification during printing, and parts with ~10 % porosity could be obtained for the coated material, compared to ~20 % porosity for the reference Cu with the same printing parameters. Raman spectroscopy and EDS analysis indicate the survival of graphene-based material inside the Cu matrix with a significant increase in the 2D peak intensity and and a decrease in the D/G peak intensity ratio. The power of the laser was limited to 160 W and significantly denser parts could not be achieved with lower scan speeds, smaller hatch spacing or double-scan strategies. Going forward, another machine with higher available laser power will be used to obtain dense parts where properties of the printed composite material can be analysed further.