Design and validation of a high-pressure laser melting system
Name
1252630570-MIT.pdf
Size
64.03 MB
Format
Adobe PDF
Checksum (MD5)
486f4cc961b0d3c8a09b0cb85cc125c8
Author(s)
Griggs, David A.(David Andrew)
Advisor(s)
A. John Hart.
Date Issued
2021
Publisher
Massachusetts Institute of Technology
Abstract
Metal additive manufacturing (AM), and in particular, laser powder bed fusion (L-PBF), is being successfully applied to diverse industrial applications. However, L-PBF demands a thorough investigation of the complex thermophysical phenomena which occur where the laser interacts with the metal powder bed. Studies of both L-PBF and laser welding show that gas dynamics, and therefore the ambient pressure, significantly impact the process and the quality of resulting parts. This thesis is motivated by an interest to investigate L-PBF at elevated ambient pressure, with the central hypothesis being that elevated pressures may decrease vaporization and melt pool turbulence, resulting in more uniform melt tracks, and thus, higher quality L-PBF parts. Therefore, this thesis presents the design and validation of a custom built high-pressure laser melting (HPLM) system which accommodates bare metal plate samples as well as manually-coated single powder bed layers. The open architecture of this testbed allows for full dynamic control of all relevant laser parameters in addition to ambient gas pressure and gas flow over the build area. Representative melt tracks and rasters on bare plate and powder are examined in order to validate system performance. Preliminary analysis concludes that pressure has a significant impact on melt pool aspect ratio and on the total amount of material melted, and that the HPLM system is capable of precision investigation of laser melting and L-PBF at pressures of up to 300 psig, considering both machine operation and gas flow dynamics. The HPLM system thus enables careful study of pressure's influence on the process windows of common L-PBF materials as well as materials that are challenging to process under ambient pressure, such as those with high vapor pressures.
Description
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, February, 2021
Cataloged from the official PDF version of thesis.
Includes bibliographical references (pages 121-124).
Subjects
Mechanical Engineering.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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