Selective laser melting of thermal pre-treated metal oxide doped aluminum oxide granules

The influence of powder bed density on the final density and microstructure of aluminum oxide parts manufactured by direct selective laser melting has been studied. Iron oxide and manganese oxide nanoparticles were used to improve laser absorption by over eighty percent. To achieve such values, flowable doped alumina granules were prepared by spray drying. Thermal treatment of the granules at 1600 ​°C and consecutive mixing with coarse alumina allowed improvement of the tapped powder densities, reaching a maximum value of 56.4% of the theoretical density. This led to laser processed parts with densities up to 98.6% measured by tomographic microscopy. Measurements with an integrating sphere and an UV-VIS-NIR spectrophotometer employing Kubelka-Munk theory show the decrease of absorptance caused by thermal pre-treatment. 3D mapping by X-ray μ-beam fluorescence contrast tomography and high resolution synchrotron powder diffraction provide information about the variation of dopant distribution and composition within the granules. [Display omitted] •Thermal pre-treatment of spray-dried alumina granules increased the powder density.•Homogeneous addition of manganese oxide or iron oxide improved the powder absorptance.•Tomographic microscopy revealed densities up to 98.6% of parts produced by SLM.•Increased powder density led to an increase of laser manufactured part density.