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Measurement of Thermal Processing Variability in Powder Bed Fusion

Published

Author(s)

Jarred C. Heigel, Eric P. Whitenton

Abstract

Laser powder bed fusion (LPBF) is an additive manufacturing (AM) technology used to manufacture high-value metal parts. The layer-by-layer nature of the process allows complex geometries and internal features, such as conformal cooling channels, to be realized. For the technology to reach its full potential, it must be capable of manufacturing precision parts. However, the precision of parts fabricated using LPBF is currently orders of magnitude worse than can be achieved using machining [1]. This is due, in part, to the distortion that arises from thermally induced residual stresses [2]. While distortion can be compensated for and/or corrected through post-processing, this is costly and not always possible for internal features. An additional challenge that LPBF and other metal AM technologies face is that in addition to creating the part geometry, the material is also created during the process. The melting of the metal feedstock powder using a laser and the rapid cooling of the solidified material, as well as the cyclic re-heating and cooling from adjacent tracks and subsequent layers, has a significant impact on microstructure and material properties [3]. Unfortunately, the material of a LPBF manufactured part is inhomogeneous due to the inconsistency of the thermal processing throughout the part. The imprecision arises from a variety of factors including scan strategy and processing conditions [4] and geometric effects, such as the reduced ability to conduct heat away from the melt pool when creating overhangs. Considering the impact on distortion, microstructure, and material performance, the thermal history of the processed material must be understood before precision geometries or materials can be manufactured using LPBF technologies. The objective of this work is to present preliminary results from in situ thermographic measurements acquired during the build of a complex part and to assess the variability of the thermal processing.
Proceedings Title
Proceedings of the 2018 ASPE and euspen Summer Topical Meeting - Advancing Precision in Additive
Manufacturing
Volume
69
Conference Dates
July 22-25, 2018
Conference Location
Berkeley, CA
Conference Title
2018 ASPE and euspen Summer Topical Meeting - Advancing Precision in Additive Manufacturing

Keywords

Additive manufacturing, powder bed fusion, laser processing, thermography, temperature measurement, cooling rate, in situ measurement
Created July 25, 2018, Updated September 6, 2018