Accuracy of surface topography measurements performed by X-ray computed tomography on additively manufactured metal parts

Additively manufactured metal parts are inherently characterized by surface topographies that are challenging to be measured due to several complexities, including: presence of undercuts and non-totally melted powder particles. Micro X-ray computed tomography has recently started to be considered as an alternative technique for topographical measurements of additively manufactured surfaces, as it is capable of measuring also non-accessible surfaces and micro-scale surface features including undercuts. In this work, a new approach to determine the accuracy of surface topography measurements performed by computed tomography is proposed and applied on Ti6Al4V specimens produced by selective laser melting. Reference cross-sectional profiles including undercuts were obtained after cutting and polishing the specimens at specific locations, by measuring the resulting cut-sections using an imaging probing system. In addition, the results of computed tomography measurements were compared with the results obtained from focus variation and confocal microscopy.