Additive Manufacturing of Metals: Microstructure, Properties and Alloy Development: Fe-based Alloys
Program Organizers: Prashanth Konda Gokuldoss, Tallinn University of Technology; Juergen Eckert, Erich Schmid Institute of Materials Science; Zhi Wang, South China University of Technology
Wednesday 2:00 PM
October 20, 2021
Room: A115
Location: Greater Columbus Convention Center
Session Chair: Rangasayee Kannan, Oak Ridge National Laboratory
2:00 PM
Binder Jet Printing of Austenitic 316L Stainless Steel: Processing, Densification, Microstructure, and Mechanical Properties: Mohammad Jamalkhani1; Amir Mostafaei1; 1Illinois Institute of Technology
Binder jet printing (BJP) refers to the technology in which metal powder is deposited layer-by-layer and selectively joined in each layer with a binder, a polymeric liquid. Sintering plays a vital role when it comes to having a final BJP product with a density of > 99%. This study focuses on examining the effect of sub-solidus and supersolidus liquid phase sintering on the densification, microstructure evolution, and mechanical properties of BJP austenitic 316L stainless steel. A near-fully densified part with density of up to 99%, as well as optimum mechanical properties (e.g., hardness up to 67 HRB, the ultimate strength of 560 MPa, yield strength of 190 MPa, and elongation up to 45%) may be attained by supersolidus liquid phase sintering. Here, a facile non-energy beam additive manufacturing method is introduced to produce stainless steel parts with microstructure and properties similar to cast alloy or powder metallurgy parts.
2:20 PM
Deformation Mechanisms in 316L Stainless Steel Fabricated by Additive and Additive + Subtractive (Hybrid) Manufacturing: Rangasayee Kannan1; Peeyush Nandwana1; Thomas Feldhausen1; 1Oak Ridge National Laboratory
In this presentation, the underlying deformation mechanisms in 316L stainless steel fabricated by additive and hybrid (additive+subtractive) manufacturing have been compared using microstructure characterization and strain hardening analysis. It was found that twinning was the dominant deformation mechanism in 316LSS produced by both additive and hybrid approaches. However, the hybrid samples have a relatively lower fraction of twins in the as-fabricated state compared to samples fabricated by a fully additive approach. The variation in twin fraction in the as-fabricated state resulted in delaying the onset of steady-state strain hardening rate to higher strain levels, thereby resulting in an overall increase in elongation to failure for the hybrid sample. The results go to show that that hybrid manufacturing has the potential to fabricate 316LSS parts with superior strength than the wrought materials and with a ductility higher than additive manufacturing and comparable to wrought materials.
2:40 PM
Influence of the Cellular Subgrain Feature in Additively Manufactured 316L Stainless Steel on Mechanical Properties: Janith Wanni1; John Michopoulos2; Ajit Achuthan1; 1Clarkson University; 2Naval Research Laboratory
Additively manufactured 316L stainless steel (316L) exhibits a greater strength than conventionally manufactured 316L without a substantial decrease in ductility. This behavior is attributed to the influence of the cellular subgrain feature present in AM 316L material. However, the mechanism responsible for the influence is not well understood or established yet. In this presentation, an experimental investigation conducted with the objective of gaining a better insight into the mechanism will be presented. The investigation primarily relies on the in-situ characterization of the heterogeneous deformation of the surface of specimens subjected to uniaxial tensile testing at microscopic length scale. It also consists of an ex-situ analysis of the deformation using SEM and AFM. Finally, a nanoindentation-based characterization will also be performed. From the characteristics of heterogeneous deformation, the mechanism responsible for the influence of subgrain feature on the mechanical properties of additively manufactured 316L is established.
3:00 PM
Microstructural Evolution in Maraging Steels: From Powder to Additive Manufacturing: Seyedamirreza Shamsdini1; Mohsen Mohammadi1; 1UNB
18Ni-300 maraging steel was studied to investigate the microstructural evolution from powder particles to additively manufactured samples using the laser powder bed fusion technique. The gas atomized powder was studied, powder particles were characterized, and the powder size distribution was measured using a mapping technique. X-ray diffraction technique was used to measure the phase fraction in powder and additively manufactured samples. Martensite and austenite phases were depicted in XRD studies. The manufacturing process proved to transform the austenite phase into martensite. Pole figures and orientation distribution functions were then shown from the XRD studies. The manufacturing process resulted in orientational grain structure with respect to building direction. Specimens were then subjected to tensile plastic deformation, and the phase fractions and the grain orientation change due to deformation were studied. Results showed that regardless of the initial texture implied through the manufacturing process, the deformation induces texture regarding the load direction.
3:20 PM Break
3:40 PM
Mechanical Properties and Metallurgical Characteristics of H13 Tool Steel Additively Manufactured in Low Vacuum and Heated Condition: Shinji Matsushita1; Hirotsugu Kawanaka1; Hyakka Nakada1; Steven Osma1; Yusuke Yasuda1; Seung Hwan Park1; 1Hitachi Ltd.
Additive manufacturing of H13 tool steel is expected to be utilized for producing casting dies with cooling channels. However, as a challenge for application of H13 tool steel to AM, H13 tool steel has high hardness after solidification and cracks are likely to occur during building. Thus, we have developed the original selective laser melting machine equipped with low vacuum system and heating device, which make it possible to build products without cracks suppressing oxidation in high temperature condition. In this study, first of all, we investigated the recoating condition in which the powders were not spattered in the low vacuum environment. Secondly, we evaluated the mechanical and metallurgical characteristics of H13 tool steel additively manufactured under low vacuum and high temperature conditions, 80℃ and 300℃. Finally, we considered the optimization of material recipe by using kernel ridge regression model, one of machine learning techniques.
4:00 PM
Nano and Macro Mechanical Properties of Additively and Traditionally Manufactured 17-4 PH Stainless Steel: Hisham Abusalma1; Mohammad Sepahi1; Sandeep Khadka1; Dana Ingalsbe1; Natalia Esparragoza1; Matthew Rosser1; Xiaoqing Wang1; Hamid Eisazadeh1; 1Old Dominion University
17-4 PH, a martensite phase dominant precipitation hardened stainless steel, exhibits a unique combination of properties such as ultrahigh strength and excellent fracture toughness. However, these properties are influenced by manufacturing techniques and heat treatments. In this study, the mechanical properties of 17-4 PH stainless steel parts made by laser powder bed fusion additive manufacturing (L-PBF-AM) method and traditionally manufactured technique are investigated using various techniques. Heat treatment was also utilized to understand its impact on the performance of parts. Tensile test and nanoindentation method are used to extract hardness, Young’s modulus, and toughness in AM and machined specimens. Results indicated that Young’s modulus and hardness of as printed parts were lower to machined parts However, heat treatment increased these properties significantly.
4:20 PM
Use of Water Atomized Powder with Non-spherical Morphology in a Laser Powder Bed Fusion Additive Manufacturing Process: Mahya Shahabi1; Tianyu Zhu1; Jagannath Jayachandran1; Sneha Prabha Narra2; 1Worcester Polytechnic Institute; 2Carnegie Mellon University
Depending on the alloy and the powder manufacturing methods, powder costs can be one of the major cost contributors in metal additive manufacturing (AM). A viable way to reduce these costs is by using relatively cheaper powders compared to gas atomized powders. Hence, the focus of this work is to demonstrate the use of powders with irregular/non-spherical morphology in the laser powder bed fusion process. We investigated the use of water atomized 17-4 precipitation hardening (PH) stainless steel powder with irregular/non-spherical morphology. Optimal deposition conditions were developed to achieve a part density comparable to samples fabricated using standard gas atomized powders. Overlap depth percentage between adjacent melt tracks was identified as the key factor for controlling porosity in the as-fabricated parts. Also, we will present results from a preliminary study on pore elimination considering the effect of thermocapillary, buoyancy, and drag force as well as the inertia of the liquid.