The New Jersey Institute of Technology's
Electronic Theses & Dissertations Project

Title:	Development of low alloy steel by direct metal laser sintering
Author:	Jelis, Elias
View Online:	njit-etd2017-017 (xviii, 104 pages ~ 5.8 MB pdf)
Department:	Committee for the Interdisciplinary Program in Materials Science and Engineering
Degree:	Doctor of Philosophy
Program:	Materials Science and Engineering
Document Type:	Dissertation
Advisory Committee:	Ravindra, N. M. (Committee chair) Lee, Eon Soo (Committee member) Nadimpalli, Siva P.V. (Committee member) Jaffe, Michael (Committee member) Clark, Stacey (Committee member) Skelton, Donald (Committee member)
Date:	2017-01
Keywords:	Laser Powder Sintering Steel Metal Additive manufacturing
Availability:	Unrestricted
Abstract:	The US Department of Defense is interested in developing, understanding, and optimizing process parameters for low alloy (4340/4140 steel) for the powder bed fusion process. Low alloy steel is used in parts where high strength and toughness are required. During parameter optimization, several aspects of the process are investigated. Powder size and morphology optimization is important for manufacturability because adequate packing is required to produce full density components. Microstructure evaluation is used in order to provide insight into parameters that lead to optimal mechanical performance and recoating performance. Influence of residual stress is evaluated with this process. Large thermal stress can lead to high distortion and deflection. A general corrosion study is conducted on direct metal laser sintered parts in order to evaluate the factors which lead to corrosion. The main objectives of this effort are to produce mechanical properties of steel that are comparable to wrought 4340 and to understand the factors which influence the qualification of the powder bed fusion process.