SYMPOSIA PAPER Published: 26 February 2022

On The Evaluation of Surface Roughness: X-Ray Tomography Reveals Hidden Details


Additively manufactured surface roughness is an inherent aspect of the process that is known to influence especially the fatigue performance of additively manufactured parts. Postprocessing is often used to improve the surface, but this is not always possible with complex shaped parts such as biomimetic and topology optimized or lattice parts, for example, where surfaces may not be accessible. It is known that scanning strategies and process parameters play an important role in improving the surface condition. The laser spot size, laser power, scan speed, and layer thickness all play critical roles. Overhang angles also have an important influence, as well as the attachment of supports (and the removal process), and finally the size of the used powder. Surface roughness evaluation is typically done by standardized methods using tactile probe or noncontact profilometers. However, some surface features that may be critical to the fatigue properties are hidden by these methods. The use of X-ray tomography allows the evaluation of additional surface features such as undercuts, preexisting cracks, and open porosity, which are not measurable by these surface-only methods. X-ray tomography is limited in resolution capability; however, it can be used with great effect on coupon samples and mechanical test parts as part of optimization and qualification processes. This work makes use of a new simplified X-ray tomography roughness evaluation method to identify important features hidden by surface probe methods. The roughness is evaluated as a case study using traditional and X-ray tomography methods for a typical laser powder bed fusion process as a function of process parameters. This methodology can be used on coupon samples to optimize the process parameters for surface finish, enhancing the as-built surface condition for improved fatigue properties.

Author Information

du Plessis, Anton
Research Group 3D Innovation, Stellenbosch University, Stellenbosch, ZA Object Research Systems, Montreal, CA
Tshibalanganda, Muofhe
Research Group 3D Innovation, Stellenbosch University, Stellenbosch, ZA
Yadroitsava, Ina
Dept. of Mechanical Engineering, Central University of Technology, Bloemfontein, ZA
Yadroitsev, Igor
Dept. of Mechanical Engineering, Central University of Technology, Bloemfontein, ZA
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Pages: 208–222
DOI: 10.1520/STP163720200094
ISBN-EB: 978-0-8031-7722-2
ISBN-13: 978-0-8031-7721-5