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Additive Manufacturing of Large-scale Metallic Components: On-Demand Oral Presentations
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee
Program Organizers: Sneha Prabha Narra, Carnegie Mellon University; Sougata Roy, Iowa State University; Andrzej Nycz, Oak Ridge National Laboratory; Yousub Lee, Oak Ridge National Laboratory; Chantal Sudbrack, National Energy Technology Laboratory; Albert To, University of Pittsburgh

Monday 8:00 AM
March 14, 2022
Room: Additive Technologies
Location: On-Demand Room

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Mechanical Response of Wire-arc Additively Manufactured LA100^TM with and without Post-print Heat-treatments: Yukinori Yamamoto¹; Sougata Roy²; Peeyush Nandwana¹; Wei Tang¹; Andrzej Nycz¹; Mark Noakes¹; Ben Schaeffer³; Badri Narayanan³; ¹Oak Ridge National Laboratory; ²Oak Ridge National Laboratory (now with University of North Dakota); ³Lincoln Electric
    LA100^TM is a low carbon and high manganese containing weld-filler steel wire which targets achieving 100 ksi tensile strength in the as-welded condition, suitable for a near-net shape component production through a wire-arc additive manufacturing technique. Because of relatively low phase-transformation temperature, the cyclic heating-and-cooling process during printing causes inhomogeneous microstructure evolution from place to place, which suggests a potential improvement of mechanical properties by applying a post-print heat treatment. The present study evaluated the effect of normalization-and-quenching and additional tempering on the mechanical properties of wire-arc additively manufactured LA100 walls, including tensile, impact toughness, and fatigue performance. The properties were correlated with the macro- and microstructures as a function of the post-print heat-treatments, and then utilized for optimization of the mechanical performance. Research sponsored by the U.S. DOE, Office of EERE, Additive Manufacturing Office, under contract DE-AC05-00OR22725 with UT-Battelle, LLC, and supported by a collaboration with Lincoln Electric.

Modified Inherent Strain Method for Wire Arc Additive Manufacturing: Wen Dong¹; Albert To¹; ¹University of Pittsburgh
    Wire arc additive manufacturing (WAAM) has drawn increasing attention due to its ability to print large metal parts. However, the large product size requires more heat input and also weakens heat dissipation, resulting in significant heat accumulation during the deposition. The present work extends the modified inherent strain method (MIS) to account for this heat accumulation and studies its influence on residual stress and distortion of parts printed by the WAAM process. For a given part, instead of using a uniform inherent strain vector over the entire part, a series of temperature-dependent strain vectors are calculated through the detailed process simulation and applied in the MIS-based part-scale simulation according to the temperature distribution of the deposit. The effect of solid-state phase transformation in WAAM-processed Ti6Al4V is also incorporated into the model when determining the inherent strains. The proposed method is experimentally validated and shows good accuracy.

Residual Stress, Microstructure and Characterization of Self-mated Repair of Inconel 718 Using Cold Spray Process: Hariharan Sundaram¹; Prasad Raghupatruni¹; ¹GE
    Inconel 718 was deposited via cold spray process on to Inconel 718 base material as a possible alternative repair of the hardware after service. A detailed characterization of the thick (2 mm) coatings was carried out, for analyzing the coating porosity, residual stress, mechanical properties including bond strength and microstructure (phase stability), in the as sprayed condition. The coating relaxation behavior and thermal stability were studied, after heat treatment at the relevant temperatures. Detailed characterization of the coating behavior, inter-diffusion characteristics with the substrate, and residual stress, enabled understanding of near net repair of the part used as a possible alternative for conventional welding or other repair processes known. The overall analysis indicated the coating to be well suited for self-mated near net shape repair applications for turbo-machinery components and indicated heat treatment improvement can lead to improved mechanical properties in these systems.

Cancelled
Thermal Fluid Dynamics of the WAAM Bead Reshaping by Adding a Scanning Laser: Xin Chen¹; Guangyu Chen¹; Jialuo Ding¹; Yipeng Wang¹; Stewart Williams¹; ¹Cranfield University
    Recent experiments showed that the WAAM bead could be reshaped by adding a lateral scanning laser, which is enormously significant in printing net-shape large-scale metal components. However, more efforts still need to be paid to the physical mechanisms of how the additional scanning laser changes the bead shape. In this work, based on our recently developed wire-feeding model, the heat transfer and fluid flow behaviours in the wire and plasma arc additive manufacturing of mild steel with and without adding a scanning laser were simulated. The calculated bead dimensions were consistent with the experiments. The simulation results showed the bead could be three times wider when adding a scanning laser with a power of 2.7 kW than no additional laser input. The results revealed convection dominates the heat transfer in the molten pool. The local Marangoni flow produced by the additional laser could be the core of the bead reshaping.

Experimental and Numerical Assessment of H13 Tool Steel Produced by Directed Energy Deposition: Sameehan Joshi; Shashank Sharma¹; Sangram Mazumder¹; Mangesh Pantawane¹; Narendra Dahotre¹; ¹University of North Texas
    Laser based directed energy deposition (L-DED) was employed for additive manufacturing of H13 tool steel. A constant laser power of 350 W was implemented during L-DED, while, the scanning speeds were varied from 5.8-14.8 mm/s. Multiscale microstructure and phase evolution observations were performed. A 3-d process model based on multi-track, multi-layer, and multiphysics methodology simulated the complex thermokinetic conditions during L-DED. Spatial variations in thermal gradients and solidification rates within a melt-pool were computationally predicted. Cellular morphology from prior solidified austenite was retained in the microstructure. Precipitates composed of carbide forming elements evolved at cell boundaries/junctions during reheating cycles experienced by the L-DED material. Retained austenite fraction decreased with an increase in the laser fluence. Processing-structure-property relationship in L-DED H13 tool steel was realized by hardness evaluation in various regions of the deposited samples. Hardness of the samples increased along the build height and as a function of laser fluence.

A High Fidelity Melt Pool Dynamics Model with Experimental Validation Results under Various Laser Power Densities and Scanning Speeds: Kyung-min Hong¹; Corbin Grohol¹; Yung Shin¹; ¹Purdue University
    This presentation covers the high fidelity welding model developed to study the melt-pool dynamics with the consideration of relevant physics and laser beam absorption via multiple reflections in the keyhole using ray tracing. The high-fidelity welding model accounts for the effects of phase change, recoil pressure, and energy loss in the form of latent heat. The transport phenomena in both the condensed (solid and liquid) and non-condensed regions (metallic vapor and ambient gas) are calculated by the governing equations of mass, momentum, and energy. In addition, the high-fidelity welding model is unique in that it also solves the conservation equation of chemical species, which is coupled with the other conservation equations to track the distributions of metallic vapor in the plume. The simulated results are compared with various NIST benchmarking test results of Inconel 625 with different laser power levels and scanning speeds.

Prediction of Large Domain Thermal History and Molten Pool Shape Using the Surrogate Modeling and Machine Learning: Corbin Grohol¹; Yung Shin¹; ¹Purdue University
    This study is concerned with predicting accurate temperature fields in a large domain using a surrogate modeling technique and machine learning. Though high-fidelity modeling has been demonstrated to provide accurate representations of the resulting geometry and temperature field, simulation of large scale as-built components is not feasible, even with massively parallelized computing. Instead, a surrogate modeling approach is demonstrated using a lower-fidelity model to extract features for use in a Gaussian process regression and implementing an active learning algorithm to determine when the high-fidelity model needs to be simulated to improve modeling results. Using such an approach, the high-fidelity model computational load can be decreased significantly, increasing calculation throughput. With this approach, accurate molten pool shapes of a large domain are predicted with affordable computational time. The validation results provide evidence that this method is effective and provides reasonable accuracy.

Constitutive Modeling of Additively Manufactured Multi-phase Steel Alloys by the Crystal Plasticity Finite Element Method: Hongguang Liu¹; Yung Shin¹; ¹Purdue University
    Metal additive manufacturing is known to produce inhomogeneous microstructures and phases. Therefore, accurate prediction of resultant mechanical properties remains a challenge. A predictive model must account for constituent phases and microstructures. Existing constitutive models are limited to the specific microstructures and the specific test conditions used. In this study, a multi-scale approach is presented to predict the material behaviors of multi-phase steels based on arbitrary phase fractions. The crystal plasticity finite element method is used to obtain the material constitutive behavior of each phase at micro-scale at various strain rates, which is validated with the experimental data or theoretical model. Then the homogenization procedure with the rule of mixture method is used to get the macro-scale constitutive behavior based on the phase fractions measured from the microstructure characterization, which is implemented into the commercial software Abaqus/Standard to simulate the process of tensile test and validated with the experimental data.

Wire Arc Processing of Stainless Steels; Microstructure and Properties: Patxi Fernandez-Zelai¹; Andrzej Nycz¹; Quinn Campbell¹; Yousub Lee¹; Michael Kirka¹; ¹Oak Ridge National Laboratory
    Large scale additive manufacturing (AM) offers significant opportunities to scale AM to larger components. Fundamentally the process science is driven by the established welding knowledge but there are still many materials challenges to be addressed prior to widespread industrial adoption. We share our recent work on arc welding AM of 316L and 17-4PH stainless steels. In 316L an extremely sharp crystallographic texture is observed with a strong {011} preference in the build direction and {001} in the travel direction. This solidified microstructure is driven by the weld pool morphology and deposition pattern. The 17-4PH material is martensitic with lathes that effectively homogenize the microstructure. Whereas the 316L exhibits anisotropic mechanical behavior, similar to that of a single crystal, the 17-4PH is isotropic. This work demonstrates that detailed characterization of deposited material is necessary for qualification of AM materials and that the behavior can be explained by the fundamental process-structure-property relations.

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