Measurement of powder bed oxygen content by image analysis in laser powder bed fusion

Costs and resource efficiency of laser powder bed fusion (L-PBF) are highly dependent on the ability to produce high quality parts with recycled powders. There is a need to control the quality of the material, which has a direct influence on the performance of the printed parts. Particles oxidation is known to increase with repeated powder recycling and can be a good indicator of powder degradation. The char-acterization of powders oxygen content is time-consuming, expensive, and usually carried out ex-situ on non-reusable quantities that are not necessarily representative of the entire feedstock. In this work, a new methodology was developed to measure the oxygen content of powders by in-line scanning of pow-der bed layers. The method takes advantage of stainless steel particles coloration related to their oxida-tion level in order to assess their oxygen concentration as a function of Red, Green and Blue channel values of image scans. The calibration procedure once carried out, several recycled powder samples were scanned and analyzed, and the determined powder beds oxygen contents were demonstrated to be in accordance with ex-situ measurements. The results highlight a new opportunity to monitor and evaluate powder degradation in-situ on powder bed layers by image analysis.(c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The quality of laser powder bed fusion (L-PBF) and its cost efficiency depend heavily on the ability to produce high-quality parts using recycled powders. To control material quality, it is important to assess particle oxidation, which increases with powder recycling and indicates powder degradation. In this study, a new methodology was developed to measure the oxygen content of powders using in-line scanning of powder bed layers. By analyzing the coloration of stainless steel particles, the oxygen concentration was determined based on Red, Green, and Blue channel values. The results demonstrate a new opportunity for in-situ monitoring and evaluation of powder degradation in powder bed layers through image analysis.