Additive Manufacturing: Advanced Characterization with Synchrotron, Neutron, and In Situ Laboratory-scale Techniques: In Situ Monitoring and Diagnostics: Directed Energy Deposition
Sponsored by: TMS: Additive Manufacturing Committee
Program Organizers: Fan Zhang, National Institute of Standards and Technology; Tom Stockman, Los Alamos National Laboratory; Tao Sun, Northwestern University; Donald Brown, Los Alamos National Laboratory; Yan Gao, Ge Research; Amit Pandey, Lockheed Martin Space; Joy Gockel, Wright State University; Tim Horn, North Carolina State University; Sneha Prabha Narra, Carnegie Mellon University; Judy Schneider, University of Alabama at Huntsville
Thursday 8:30 AM
February 27, 2020
Room: 8
Location: San Diego Convention Ctr
Session Chair: Sneha Narra, Worcester Polytechnic Institute
8:30 AM Invited
On In-situ Monitoring of Geometry, Temperature, and Plume Behavior in Laser-based, Powder-blown Directed Energy Deposition Additive Manufacturing: Abdalla Nassar1; Christopher Stutzman1; Edward Reutzel1; Dustin Seltzer2; Jeffrey Schiano2; Stephen Brown1; Wesley Mitchell1; 1Applied Research Lab at Penn State; 2Pennsylvania State University
Laser-based, powder-blown directed energy deposition (DED) is among the most versatile of additive manufacturing (AM) processes. Using DED, high-value, metal components can be fabricated or repaired using a single or a combination of material systems. Unfortunately, DED processing involves complex interactions between laser energy, melt, plume, and powder. In-situ monitoring provides a pathway for both elucidating these complex interactions as well as for documenting build quality in real time. However, monitoring of key processing parameters is neither straightforward nor easy. Here, recent strategies for monitoring build geometry, temperature and plume behavior are presented and common challenges, particularly plume interference, are addressed.
8:55 AM
In-situ Synchrotron X-ray Imaging of Titanium Alloy Powder Sintering during Laser Blown Powder Directed Energy Deposition: Lorna Sinclair1; Yunhui Chen2; Sebastian Marussi2; Samuel Clark1; Chu Lun Alex Leung2; Saurabh Shah2; Robert Atwood3; Thomas Connolley3; Martyn Jones4; Gavin Baxter4; Peter Lee2; 1University College, London; 2University College London; 3Diamond Light Source Ltd.; 4Rolls-Royce plc.
Laser Blown Powder Directed Energy Deposition (LBP-DED) is a promising technique for rapid part production, coatings, and repair applications. However, metal vapour plumes and oxides on the powder surface can result in lightly sintered powder adhering to the surface during titanium alloy builds. To understand this phenomenon, a process replicator was used to carry out in situ and operando investigations of the process using high speed synchrotron X-ray imaging. A range of process parameters was explored to investigate the conditions under which sinter occurred. Several hypotheses for this mechanism were tested, including aluminium vapour deposition onto the powder, oxide formation, and direct heating leading to surface wetting. The results suggest probable mechanisms, and illustrate that the sintered powder can be mitigated when appropriate parameters are used.
9:15 AM
Capturing Marangoni Flow via Synchrotron Imaging of Laser Blown Powder Directed Energy Deposition: Samuel Clark1; Yunhui Chen1; Lorna Sinclair1; Chu Lun Alex Leung1; Sebastian Marussi1; Robert Atwood2; Martyn Jones3; Gavin Baxter3; Peter Lee1; 1University College London; 2Diamond Light Source Ltd; 3Rolls-Royce plc
Marangoni flow has a substantial influence upon the quality of additively manufactured and repaired aerospace components via laser blown powder directed energy deposition (LBP-DED). However, Marangoni flow is rarely quantified due to the opacity of liquid metals and the necessity for in situ evaluation of this time-transient phenomenon. Here we report the findings of our synchrotron X-ray radiography flow tracking experiments. Dense, highly attenuating tungsten particles are seeded within an aerospace alloy powder feedstock. Due to the large magnitude of the Marangoni flow, rather than perform frame-to-frame tracking, we exploit the elongated streaks as the tracking particle move throughout each exposure time. Through evaluation of the length and path of the streak patterns we quantify the velocity and direction of melt pool flow. This work also provides new insights into how Marangoni flow interacts with pores entrapped within the melt pool, providing valuable process guidance and informing Multiphysics models.
9:35 AM Invited
In-situ Process Monitoring and Diagnosis via Machine Learning of Thermal Imaging Streams: Linkan Bian1; 1Mississippi State University
One current challenge in Laser Based Additive Manufacturing (LBAM) is the potential defects and structural integrity of fabricated parts. To improve quality of fabricated parts, accurate predictions of part quality are needed. We develop a novel machine learning framework that accurately predicts the physics and mechanical properties well within LBAM tolerance limits by considering the local heat transfer. The central hypothesis is that terabytes of thermal imaging data generated during the LBAM fabrication is highly correlated to the relevant part properties, and thus can be used to predict the distribution of internal defects and external geometric characteristics. To achieve this goal, efficient methodology is needed to extract relevant features based on big thermal data. Our tensor-based machine learning approach not only gives highly accurate NDE for the fabricated parts but also provide a realistic approach for handling big data generated from parts with large size and complex geometries.
10:00 AM
In-situ and Operando X-ray Imaging of the Laser Blown Powder Directed Energy Deposition Process: Yunhui Chen1; Samuel Clark1; Lorna Sinclair1; Chu Lun Alex Leung1; Sebastian Marussi1; Robert Atwood2; Martyn Jones3; Gavin Baxter3; Peter Lee1; 1University College London; 2Diamond Light Source; 3Rolls-Royce plc
Laser Blown Powder Directed Energy Deposition (LBP-DED) is one of the principal additive manufacturing techniques for repair applications. However, an increased fundamental understanding of the process is required to avoid such features as porosity, lack of fusion and cracking. This study provides new insights into the manufacturing process using a LBP-DED process replicator that fits onto a synchrotron beamline enabling in situ and operando X-ray imaging. This system provides a better fundamental understanding of the relationships between process parameters and feature formation. Laser-matter interaction and building efficiencies are monitored in situ during multi-layer build conditions using SS316 and Ti6242. Laser power, powder feed-rate and build speed are evaluated for their contributions to the build quality. Micro-CT and electron microscopy are used to verify the in situ observations. These insights reveal how to control the LBP-DED process to tailor the properties of the components produced.
10:20 AM Break
10:40 AM Invited
In-situ 3D Digital Image Correlation and Thermal Imaging for Process Monitoring in Laser Directed Energy Deposition (L-DED): James Haley1; Brian Jordan1; Ross Cortino1; Ryan Dehoff1; Vincent Paquit1; 1Oak Ridge National Laboratory
In laser-based metal Additive Manufacturing (AM), detrimental part distortion is a natural consequence of the accumulated stresses and strains from the complex, time variant thermal field produced by the scanning laser. In this work, these distortions are directly quantified through in-situ, real time 3D Digital Image Correlation (DIC), and are mapped concurrently with the thermal field measured from infrared imaging. Thermal expansion and contraction of deposited material layer-to-layer produces variable degrees of hot and cold work, which competes with annealing from subsequent laser passes to produce the final microstructure of the deposited component. The diverse influences of different geometries and scan patterns on the strain evolution of a component are explored in detail. 3D DIC with infrared imaging provides an inexpensive and deep dataset for model and control algorithm development while maintaining a high degree of independence from part geometry and build size.
11:05 AM
In-process Monitoring of Porosity in Additive Manufacturing: Bin Zhang1; Shunyu Liu1; Yung Shin1; 1Purdue University
This work describes in-process porosity monitoring for additive manufacturing processes based on deep learning and a real time weld pool monitoring system. A high-speed digital camera was mounted coaxially to the laser beam for in-process sensing of melt-pool data, and convolutional neural network models were designed to learn melt-pool features to predict the porosity attributes in built specimens during additive manufacturing. The convolutional neural network (CNN) models with a compact architecture, part of whose hyperparameters were selected through cross-validation analysis, achieved a classification accuracy of 91.2% for porosity occurrence detection in the direct laser deposition of sponge Titanium powders and presented predictive capacity for micro pores below 100 µm. For local volume porosity prediction, the model also achieved a root mean square error of 1.32% and exhibited high fidelity for both high porosity and low porosity specimens.
11:25 AM
In-situ Synchrotron Measurements of Microstructure Development at Fusion Boundary in Wire Feed AM of Ti-6Al-4V: Nathan Johnson1; Donald Brown2; John Carpenter2; Aaron Stebner1; 1Colorado School of Mines; 2Los Alamos National Laboratory
Wire feed additive manufacturing is a unique advanced manufacturing technique that allows large scale, fast manufacturing of near net components due to its fast deposition rate and the relatively large amount of material deposited at once. These advantages also create large thermal gradients during layerwise deposition, which can lead to grain recrystallization and regrowth at the boundary layer, diffusion of alloying species in multiphase materials, and texture development throughout the part. Experiments conducted at the Advanced Photon Source characterized Ti-6Al-4V microstructure development at the fusion boundary between layers in wire feed AM of Ti-6Al-4V. Phase fractions, lattice strains, and texture development were monitored during multipass manufacturing of a wall structure. Microstructure development was studied as a function of the rate of material deposition, the time between depositions, and the amount of material deposited. Texture was characterized during the build process to monitor grain re-orientation during the build process.
11:45 AM
High-speed X-ray Imaging of Powder Deposition of Composite Materials in Additive Manufacturing: Sarah Wolff1; Niranjan Parab1; Benjamin Aronson2; Benjamin Gould1; Aaron Greco1; Tao Sun1; 1Argonne National Laboratory; 2Penn State University
Directed energy deposition additive manufacturing is a flexible process to fabricate parts of dissimilar materials, including functionally graded materials and metal matrix composites (MMC's). This talk will discuss some of the results from a lab-scale deposition process observed with the high-speed imaging synchrotron beamline at Argonne National Laboratory’s Advanced Photon Source. In-situ imaging of deposited particles shows how these particles incorporate into the melt pool. Deposited particles include a variety of ceramics and coated particles, which flow into a laser-induced melt pool of a titanium, aluminum or steel alloy. Results show how velocity and injection depth of these particles can influence the overall additively built part. With control and flexibility during fabrication, these new materials can exhibit greater strength, decreased density, and improved thermal properties compared to those of conventional materials.