New method to evaluate the accuracy of CT surface topography measurements of additively manufactured metal parts

Surface topographies of metal additive manufactured components are inherently characterized by the presence of complex surface characteristics (e.g. re-entrant features), which are not accessible by contact or optical techniques. Micro X-ray computed tomography has been demonstrated capable of measuring non-accessible surfaces and micro-scale surface features, including undercuts. In this work, an innovative approach for evaluating the accuracy and establishing the traceability of surface topography measurements obtained by X-ray computed tomography is presented. Reference samples produced by selective laser melting of Ti6Al4V were specifically designed in order to acquire reference cross-sectional surface profiles representing the actual morphology (including re-entrant features) using an imaging probing system. Surface topographies were measured on these samples by X-ray computed tomography, confocal microscopy and focus variation. Moreover, the effect of different voxel dimensions on the accuracy of surface topography measurements performed by X-ray computed tomography was investigated.