Additive Manufacturing: Materials Design and Alloy Development IV: Rapid Development: Ferrous Alloys
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee, TMS: Integrated Computational Materials Engineering Committee
Program Organizers: Behrang Poorganji, Morf3d; Hunter Martin, HRL Laboratories LLC; James Saal, Citrine Informatics; Orlando Rios, University of Tennessee; Atieh Moridi, Cornell University; Jiadong Gong, Questek Innovations LLC
Wednesday 2:00 PM
March 2, 2022
Room: 261A
Location: Anaheim Convention Center
Session Chair: Atieh Moridi, Cornel
2:00 PM
In-situ Tempering of Ferrous Martensite during Laser Powder Bed Fusion: William Hearn1; Kristina Lindgren1; Eduard Hryha1; 1Chalmers University of Technology
To date, in-situ tempering of ferrous martensite during Laser Powder Bed Fusion (L-PBF) is a topic that remains poorly understood. This is primarily due to the non-equilibrium nature of L-PBF that leads to a complex thermal history. In this work, ferrous martensite in a L-PBF produced Fe-0.45C alloy was analyzed via hardness, OM, SEM, TEM and APT. These analyses found martensite to have a “quenched-like” state when initially deposited, with carbon segregating to lath boundaries and to dislocations. The most significant tempering of this “quenched-like” martensite occurred during subsequent layer melting, specifically within the heat affected zone. As said tempering led to the precipitation of vast carbide networks (at the lath boundaries) as well as a noticeable reduction in martensite hardness.
2:20 PM Cancelled
Developing High-temperature High-strength Laser Powder-bed Fusion Austenitic Steels: Sebastien Dryepondt1; Kinga Unocic1; Rangasayee Kannan1; Peeyush Nandwana1; Marie Romedenne1; Patxi Fernandez-Zelaia1; Michael Lance1; Arun Devaraj2; Jia Liu2; 1Oak Ridge National Laboratory; 2Pacific Northwest National Laboratory
The formation of sub-grain cellular structures in austenitic steels such as 316L fabricated by laser powder bed fusion (LPBF) due to extremely fast cooling rates is now well documented. Such a cellular structure offers the opportunity to develop new high strength austenitic alloys with the formation of a high density of strengthening nano precipitates because of the high dislocation density in the cellular walls. We will demonstrate that the formation of nano carbides or carbonitrides in LPBF 310 or 347-type steels can result in creep properties at 700-800°C along the build direction three to six times higher than the creep properties of cast counterparts. The lower creep strength observed perpendicular to the build direction was attributed to the elongated cells and elongated grains along the build direction. Strategies to develop LPBF-specific austenitic steels with excellent creep and oxidation resistance at T>700°C will be discussed.
2:40 PM Invited
High Strength Fe-C-Cu Alloys for Laser Powder Bed Fusion: Andrew Bobel1; Louis Hector1; Lee Casalena2; 1General Motors; 2Thermo Fisher Scientific
Two alloys from the Fe-C-Cu system were designed and evaluated as potential high strength non-stainless steel replacements for printable 17-4 PH stainless steel in laser powder bed fusion (LPBF). A computational materials design approach was employed to determine Ni and Co free printable compositions. Custom gas atomized powders were acquired and characterized. Parameter development was performed to obtain specimens with consolidation greater than 99.8% density. A single step heat treatment was developed capable of acting as both a stress relief and strengthening treatment thereby reducing post-processing time and cost. SEM and STEM revealed the heat-treated microstructure to be lath martensite with 2.6-2.8 nm diameter Cu precipitates, the same as previously reported critical diameters for BCC Cu strengthening. Tensile tests demonstrated that yield strengths of both Fe-C-Cu alloys (1208 and 1274 MPa) were comparable to 17-4 PH (1288 MPa).
3:00 PM
Additive Manufactured Stainless Steel Nanocomposites with Uniform Dispersion of Nanoparticles: Minglei Qu1; Luis Izet Escano1; Qilin Guo1; Lianyi Chen1; 1University of Wisconsin-Madison
Metal matrix nanocomposites (MMNCs) with uniform distribution of nanoscale ceramic particles can show dramatically improved mechanical properties as compared to the matrix materials. However, when the size of the nanoparticles is small and the volume fraction of nanoparticles is high, it is very difficult to disperse them uniformly in the metal matrix. Here we report the dense stainless steel nanocomposites with uniform distributed ceramic nanoparticles were successfully fabricated by ball milling and selective laser melting (SLM). Detailed microstructure characterization and analysis reveal that the dispersion of nanoparticles in the SLMed sample strongly depends on the dispersion of nanoparticles in the feedstock powders. Our research provides a promising approach to manufacture MMNCs with uniform dispersion of nanoparticles by additive manufacturing process.
3:20 PM Break
3:35 PM
Melt Pool Scale Modeling of Solidification Kinetics and Its Effects on Stainless Steel Microstructures for Laser Powder Bed Fusion: Joseph Aroh1; P. Chris Pistorius1; Anthony Rollett1; 1Carnegie Mellon University
Laser Powder Bed Fusion (LPBF) builds components by using a rastering laser which produces microstructures comprised of thousands of repeating weld pools. Due to the rapid speed of the welds in LPBF, nonequilibrium effects such as metastable austenitic solidification and solute trapping may occur in austenitic stainless steels because of solidification kinetics. Because of the self-evident importance for microstructural prediction and control in printed alloys, a computational framework consisting of a thermal model, computational thermodynamics, and dendrite growth kinetics was developed for several stainless steel alloys. The output of this pipeline was compared to both in situ synchrotron x-ray diffraction experiments and ex situ microstructural characterization of cross-sectioned melt tracks. This work aims to elucidate the location dependent microstructural evolution of solidification features at the melt pool level to inform future alloy compositions, laser parameters, and scan strategies tailored specifically for the LPBF process.
3:55 PM Cancelled
CANCELLED: Microstructure and Mechanical Properties of a Multipurpose High-strength High-toughness Martensitic Steel Produced via Selective Laser Melting: Amir Farkoosh1; Daniel Bechetti2; Matthew Sinfield2; David Seidman1; 1Northwestern University; 2Naval Surface Warfare Center Carderock (NSWCC) Division
In recent years, several steel design activities have been initiated to develop alternatives to the high yield (HY) and high strength low alloy (HSLA) steels with improved mechanical properties, producibility, and weldability. Born out of these research efforts is a novel multipurpose low-carbon 10 wt.% Ni martensitic steel, which exhibits high strengths, high toughnesses, and excellent ballistic resistance at ambient and cryogenic temperatures. In this study, we have utilized laser powder bed fusion to additively manufacture a variant of this steel. Excellent mechanical properties: a tensile yield strength of 1150 MPa and 22% elongation were achieved, demonstrating superior mechanical properties to those of conventional counterparts. We utilize synchrotron X-ray diffraction, electron backscatter diffraction (EBSD), and local-electrode atom-probe tomography (LEAP) to study the microstructural features of this AM steel over hierarchical length scales. We discuss the solidification behavior as well as the strengthening and toughening mechanisms in this novel steel.
4:15 PM
Printability and Defects in Steels Printed by Laser Powder Bed Fusion: Amaranth Karra1; Yining He1; Sraavya Ranga1; Maarten de Boer1; Bryan Webler1; 1Carnegie Mellon University
This study examines the melt pool geometry and microstructure of low alloy steels produced by laser powder bed fusion (LPBF) additive manufacturing. Single melt tracks over a range of laser power and travel speeds were made on six plates with different low alloy steel compositions. Tracks were also made with and without 4130 steel powder. Melt pool geometry and microstructure were characterized. The experimental results were used to validate heat transfer model-based predictions of melt pool geometry and literature criteria used to rank hot cracking susceptibility. The results show how single-track experiments and models can be used to assess the ability to print a range of low alloy steel compositions with minimal cracking and other defects.