Additive manufacturing by selective laser melting (SLM) allows significant flexibility in obtaining components with complex morphologies, which usually require finishing to correct the geometric distortions and roughness inherent in the process. This paper investigated surface quality by milling and reaming deep holes into ducts obtained by SLM technology. For this purpose, tools with different characteristics were tested, with a reaming stage necessary to obtain roughness levels of less than one μm. Dimensional distortions in SLMed ducts led to substantial variability in axial cutting forces. The helix angle of the endmill had a significant influence on the axial cutting force and roughness.
A Rietveld study for three ceramic pigments is presented. Two commercial black ceramic pigments, belonging to the (Cr x Fe 1Àx ) 2 O 3 family, are shown to be single crystalline phase with a negligible amorphous phase content. This conclusion is drawn from the existence of a unique crystalline phase and from the analysis of the values of the unit cell parameters. Furthermore, a much complex laboratory-prepared brown ceramic pigment has also been studied. This sample was synthesized by adding Al 2 O 3 and MgO dopants in small quantities, below 3 wt%, to the previous system. The Rietveld analysis has shown the stabilization of two corundum structures with a compositions close to Cr 0.50 Fe 1.50 O 3 and Al 0.30 Cr 1.70 O 3 , plus a spinel structure with composition close to MgCr 2 O 4 . An aluminum-rich amorphous oxide phase in low percentage is needed to balance the chemical analysis derived from the Rietveld study and that from XRF. Full mineralogical phase analyses of commercial pigments, plus the required solubility tests, may allow narrowing down of the number of toxicity tests required by REACH Int.
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