Porosity Measurements and Analysis for Metal Additive Manufacturing Process Control

• Published in: Journal of research of the National Institute of Standards and Technology Vol. 119; no. 1; pp. 494 - 528
• Main Authors: Slotwinski, John A., Garboczi, Edward J., Hebenstreit, Keith M.
• Format: Journal Article
• Language: English
• Published: United States National Institute of Standards and Technology 2014; [Gaithersburg, MD] : U.S. Dept. of Commerce, National Institute of Standards and Technology
• Subjects: 3D printing; Management; Measurement; Mechanical properties; Metal products; Methods; Porosity; Process control; Production management; Archimedes; Direct Metal Laser Sintering; additive manufacturing; X-ray computed tomography; cobalt-chrome; ultrasonic NDT; porosity; powder bed fusion
• ISSN: 2165-7254; 1044-677X; 2165-7254
• DOI: 10.6028/jres.119.019

Additive manufacturing techniques can produce complex, high-value metal parts, with potential applications as critical metal components such as those found in aerospace engines and as customized biomedical implants. Material porosity in these parts is undesirable for aerospace parts - since porosity could lead to premature failure - and desirable for some biomedical implants - since surface-breaking pores allows for better integration with biological tissue. Changes in a part's porosity during an additive manufacturing build may also be an indication of an undesired change in the build process. Here, we present efforts to develop an ultrasonic sensor for monitoring changes in the porosity in metal parts during fabrication on a metal powder bed fusion system. The development of well-characterized reference samples, measurements of the porosity of these samples with multiple techniques, and correlation of ultrasonic measurements with the degree of porosity are presented. A proposed sensor design, measurement strategy, and future experimental plans on a metal powder bed fusion system are also presented.