2023 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2023): Process Development: Directed Energy Deposition and Cold Spray
Program Organizers: Joseph Beaman, University of Texas at Austin
Monday 1:30 PM
August 14, 2023
Room: 410
Location: Hilton Austin
Session Chair: Frank Liou, Missouri University of Science and Technology
1:30 PM
Electroslag Strip Cladding for Additive Manufacturing: Adam Stevens1; Paritosh Mhatre1; Christopher Masuo1; William Carter1; Jesse Heineman1; Rangasayee Kannan1; Andrzej Nycz1; Nikolaos Tsiamis1; Sudarsanam Babu1; Brian Post1; 1Oak Ridge National Laboratory
Electroslag strip cladding is used industrially to apply corrosion-resistant inner surfaces to process vessels in the chemical industry and elsewhere. Cladding deposition rate and coverage area are subject to continuous industry development to improve the process economics, and therefore the process is uniquely suited to high-throughput additive manufacturing of large metal structures. We report preliminary experiments utilizing an electroslag strip cladding system for high-throughput metal additive manufacturing, including measured build rates, process conditions, and metallurgical characterization of multi-layer prints.
1:50 PM
Process Strategy and Geometrical Distortion of Heat-treated 17-4PH Stainless Steel Produced by Interleaved Machining and Blown-powder DED: Lauren Heinrich1; Kenton Fillingim1; Rangasayee Kannan1; Peeyush Nandwana1; Thomas Feldhausen1; 1Oak Ridge National Laboratory
Hybrid manufacturing systems incorporate subtractive and additive manufacturing within one build volume enabling interleaving between the two processes. However, the interleaving of these two processes has been found to create geometric misalignment between the interleaved steps due to the complex thermal cycling of the hybrid process. To investigate this phenomena, four differing interleaving strategies were applied to a 17-4PH stainless steel planar wall. Different rough and finish machining scheduling strategies were used to determine the best interleaving strategy for optimal geometric accuracy. Of the four walls, the wall that was machined at a distance away from the recently deposited material was found to have the highest dimensional accuracy. To simulate real-world applications, subsequent heat treatments were applied to three of the walls to better understand the effect that heat treatment after final machining has on geometrical accuracy. This result will better enable the accurate manufacture of interleaved hybrid manufactured components.
2:10 PM Cancelled
Structural Integrity Assessment of Cold Spray Repaired High-strength Aluminium Alloy 7075 Specimens: Ali Bakir1; Xiang Zhang2; Matthew Dore3; Kashif Khan2; Phil McNutt4; 1Coventry University/NSIRC, TWI Ltd.; 2Coventry University; 3Conventry University/TWI Ltd.; 4TWI Ltd.
Cold spray (CS) has seen an emerging role in repair applications, especially for temperature- and oxidation-sensitive materials. Despite its advantages, the structural integrity of CS repaired materials remains a concern due to the porosity, poor inter-particle bonding, and lack of data and standards. In this study, the mechanical performance of CS repaired samples under static and cyclic loading is being investigated. Different powder heat-treatment conditions and repair geometries are used to improve the deposition performance and structural integrity. Under tensile loading, the CS repair failed and started delaminating at around 1% elongation, whereas the specimens continued carrying tensile loading up to 7% elongation before the complete fracture, which is 50% less than the wrought material performance. Conversely, the high cycle fatigue life of the repaired samples is similar to the wrought ones, exceeding 10 million cycles at 200MPa. The common observation for all repaired samples was the fatigue crack initiated at the substrate-CS interface and propagated towards the substrate.
2:30 PM
Side on Plasma Emission Spectroscopy of TiAl6V4 During Laser Scanning: Ethan Sprague1; Nicholas Calta1; Erik Busby1; 1Lawerence Livermore
Significant focus has been placed on in-situ diagnostics for powder-based additive manufacturing, like Powder Bed Fusion (PBF) and Directed Energy Deposition (DED), using tools such as layer imaging and pyrometry over the last decade. Plasma Emission Spectroscopy is a technique which uses the spectra of the plasma plume which forms directly above the laser-metal interaction zone to study the sample below. A series of high-speed, side-on, and height-resolved spectra are taken for laser scanned TiAl6V4 plate, such that the spectra can be resolved in time and at 7 different heights above the melt pool. This data can be used to calculate the plasma temperature at different heights above the melt pool and study the stability of the plasma itself. Results show plasma temperatures generally decline with increased distance from build plate, and a high sensitivity to atmospheric quality of both plasma intensity and temperature. Prepared by LLNL under Contract DE-AC52-07NA27344.
2:50 PM
Role of In-situ Monitoring Technique for Digital Twin Development using Direct Energy Deposition: Melt Pool Dynamics and Thermal Distribution: Sung-Heng Wu1; Usman Tariq1; Ranjit Joy1; Muhammad Arif Mahmood2; Frank Liou1; 1Missouri University of Science & Technology; 2Intelligent Systems Center
Direct energy deposition (DED) is a promising additive manufacturing technique that enables the fabrication of complex structures with excellent mechanical properties. However, the quality of the final product depends on several parameters, including melt pool dynamics and thermal distribution. For process monitoring and continuous improvement of digital twins, in-situ monitoring allows real-time tracking of these parameters, providing valuable data for process optimization. However, existing monitoring methods are limited in their accuracy due to emissivity issues. To address this challenge, a visual spectrum camera has been tested for real-time process monitoring via a dual-wavelength technique. Based on the analyses, the area and thermal distribution inside the melt pool can be estimated accurately. The data from the camera can be integrated into a digital twin’s continuous improvement, providing efficiency and reducing manufacturing costs.
3:10 PM Break
3:40 PM
Influence of Substrate Temperature on the Formation of Individual Weld Paths during Laser Cladding (LMD) when Processing 316L.: Stefan Gnaase1; Christian Bödger1; Dennis Lehnert1; Thomas Tröster1; Robin Rohling1; 1Universität Paderborn / Lehrstuhl für Leichtbau im Automobil
Additive manufacturing by means of laser metal deposition (LMD) of metals holds high application potential due to the simple process scaling with regard to the production of large and complex three-dimensional structures. One of the central process variables to be considered is the component heat. The thermal energy supplied by a laser during the manufacturing process leads to different temperatures on the surface to be welded. This can lead to deviating welding results with otherwise constant process parameters. The investigations aimed at in this work shall contribute to the understanding of the influence of the substrate/part heat on the LMD process result and bring solutions for the correction of possible deviations of the welding result. For this purpose, individual weld tracks with different process parameters on substrates with controlled temperature levels will be produced and analyzed to formulate a model for the prediction of the weld result.
4:00 PM
Impact of Powder Deposition Parameters on Powder Catchment Efficiency in Laser Directed Energy Deposition: Colin Ancalmo1; Sneha Narra1; 1Carnegie Mellon University
Blown powder laser directed energy deposition (L-DED) is subject to low end-to-end material efficiencies resulting from the yield of gas atomized powder below 150μm and in-process powder catchment efficiencies (usually < 50%). These inefficiencies become important as feedstock procurement represents about 20% of the cost and 30% of the energy consumed for typical parts. Higher catchment efficiencies require smaller powder spot diameters for a fixed melt pool, and powder spot diameter is influenced by powder mass flow rate, nozzle carrier gas flow rate, and nozzle standoff distance. However, the relationship between these powder deposition parameters and catchment efficiency is not known. This work uses low-cost imaging and computer vision-based feature extraction to capture powder spot diameter for AISI 420 powder under different powder deposition parameters. The results from deposition experiments will determine whether powder deposition parameters can be optimized for increased powder catchment efficiency.
4:20 PM
Experimental Study of Cryogenic Directed Energy Deposition Conducted at -20°C: Wei Li1; Kishore Nagaraja1; Benquan Li1; 1University of Texas at Dallas
Ambient temperature has a great influence on directed energy deposition (DED), such as temperature gradient, cooling rate, and grain evolution. Currently, the DED is only performed under laboratory conditions (20°C to 25°C). So far, the DED has not been explored specifically under low temperature or cryogenic conditions. This experimental study fills this gap. In this work, the ambient temperature of DED (including substrate) was chilled to -20°C. The authors printed three thin-wall samples with stainless steel 316L powder at this cold condition. As comparative test, another sample with same geometry and material was printed with same DED parameters at room temperature (20°C). The results show some interesting findings. The sample height and molten pool size (-20°C) are larger than the sample printed at 20°C. Additionally, the hardness values of samples printed at -20°C are greater than those printed at room temperature. The tensile tests showed the -20°C samples had better mechanical properties.
4:40 PM
Embedding Fiber Optic Sensors in Metal Components via Direct Energy Deposition: Elias Snider1; Rony Saha1; Cesar Dominguez2; Jie Huang1; Douglas Bristow1; 1Missouri University of Science and Technology; 2Los Alamos National Laboratory
Fiber optics are useful as strain and temperature sensors in a variety of applications involving high-value parts. Embedding fiber optic sensors into end-use parts can allow for real-time strain and temperature monitoring of these parts in extreme conditions. Direct energy deposition processes have distinct advantages for producing parts in high-value embedded sensing applications, however, ensuring survival of the optical fiber during embedment is challenging. A method of fiber embedment using high-temperature ceramic adhesives is presented as a flexible method of embedding fiber optic sensors into end-use parts such as to preserve fiber transmission and sensor integrity. Example specimens are presented and functionality of sensing capabilities is demonstrated.