2024 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2024): Materials: Metals IV
Program Organizers: Joseph Beaman, University of Texas at Austin
Wednesday 8:00 AM
August 14, 2024
Room: Salon B
Location: Hilton Austin
Session Chair: Mahemaa Rajasekaran, EOS North America
8:00 AM
Effect of Two Different Point-Based Melt Scanning Strategies on the Microstructure of As-Built IN718 Parts Fabricated via EB-PBF System: Shadman Nabil1; Cristian Banuelos1; Gael Fierro1; Michael Madigan2; Sammy Tin2; Edel Arrieta1; Ryan Wicker1; Francisco Medina1; 1W.M. Keck Center for 3D Innovation; 2University of Arizona
Metal additive manufacturing has become an integral part of the modern aerospace and defense industry. Technologies such as powder bed fusion and direct energy deposition have reshaped these sectors. However, challenges like anisotropy and process-related defects still prevent the direct use of printed parts without post-processing. Electron beam powder bed fusion (EB-PBF) is well known for allowing builds at elevated temperatures and eliminating the need for stress relief. However, EB-PBF parts also experience epitaxial growth in the build direction, which causes anisotropy. This research explores two scanning strategies with spot melting techniques—stochastic and single directional—to fabricate IN718 parts using EB-PBF. After fabrication, the samples were analyzed using EBSD to evaluate grain formation in the build direction. The findings suggest that point-based melting, guided by these strategies, can affect the microstructure in the build direction. This advancement offers potential for tailoring controlled parts in future applications.
8:20 AM
Hot Isostatic Pressure Study of Microstructure on Electron Beam Melting Tungsten: Guillermo Ornelas1; Javier Lares1; Francisco Medina1; Kurtis Watanabe1; Edel Arrieta1; Ryan Wicker1; 1University of Texas at El Paso
Tungsten has a wide range of uses thanks to its high melting point and hardness. Often in literature, it is rare to find data about crack-free tungsten specimens and their manufacturing process. This project aims to study the effects on the microstructure of crack-free tungsten manufactured with Electron Beam Melting after going through three different Hot Isostatic Pressure cycles, performed at constant pressure and different temperatures. This evaluation was performed in terms of how grain size and defect content are affected when being exposed to three different HIP cycles. Furthermore, all specimens were manufactured using the same parameters and in the same batch. Upon optical microscopy, specimens showed a higher amount of defect formation which may be attributed to temperature variation between specimen formation, leading to unsuccessful melting of some tungsten particles. A comparative analysis of the micrographs obtained is performed to determine the effect of the Hot Isostatic Pressure.
8:40 AM
Laser Powder Bed Fusion Copper: Post-Processing, Structure, Property Relationships: Rachel Paddock1; Pouria Khanbolouki1; Saniya LeBlanc2; Michael Cullinan1; Mehran Tehrani3; 1The University of Texas at Austin; 2The George Washington University; 3The University of California at San Diego
Copper is used for a variety of electrical and thermal applications due to its exceptional physical and mechanical properties. There is a growing interest in alternatives to manufacture intricate copper parts. Additive manufacturing not only offers a substitute to traditional manufacturing methods, but also allows for optimizing designs that are otherwise difficult or impossible to make. In this research, we made copper samples using an EOS M280 laser powder bed fusion (LPBF) system. One of the greatest challenges with using LPBF for copper is the undesired structure and low density of the printed parts. To combat this challenge, we subjected the samples to annealing or hot isostatic pressing (HIP) to improve the material’s properties. This research highlights the electrical, thermal, and mechanical properties and correlates these results to the microstructure of the copper samples. Based on these results, recommendations are given for printing and post-processing copper using LPBF.
9:00 AM Cancelled
Accelerated Recyclability Assessment of 316L using Laser Powder Bed Fusion and Ultrasonic Atomisation in a Revert Loop: Edward Palmer1; Shahin Mehraban1; Daniel Butcher1; Gavin Stratford2; Nicholas Lavery1; 1Swansea University; 2LSN Diffusion
The ability to regenerate high-quality powder from printed components offers economic and environmental advantages in additive manufacturing (AM). Previous ageing studies re-using powder show relatively little impact with numerous cycles, allowing powder revert recycling strategies to account for longer shelf life. However, with growing industrial uptake of AM, there is a need to consider recycling strategies which consider both powder revert and waste material (e.g. powder at end of life, support structures and components), minimising environmental impact and promoting the circular economy of metal powders.This study investigates the recyclability of 316L parts produced via Laser Powder Bed Fusion (L-PBF) by repeatedly building and directly re-atomising parts using ultrasonic powder atomisation. The re-atomised powder is compared to the virgin powder for compositional (including oxygen and nitrogen), morphological and rheological changes. Printed parts made from the re-atomised powder are compared to virgin counterparts for changes in microstructure, hardness, and density.
9:20 AM
Laser Powder Bed Fusion of High-Strength Aluminum Matrix Composites: Ethan Parsons1; 1MIT Lincoln Laboratory
The thermomechanical properties of particle-reinforced metal matrix composites (MMCs) are attractive for high-performance defense and space applications, but fabrication of MMC components with conventional methods is difficult, costly, and typically limited to components with simple geometry. Additively manufacturing particulate MMCs with laser powder bed fusion (LPBF) would be an ideal method, but the laser consolidation of these materials has been unsuccessful in matching the properties of conventionally-produced MMCs. The challenges include hot cracking of the matrix, spreading the heterogeneous powder, distributing small ceramic particles, and forming a strong bond between the metal and the ceramic. Here, by mechanically alloying high-strength aluminum alloys and ceramic particles, we manufacture aluminum composite powders with morphology tuned for AM process conditions. Using LPBF, we achieve dense consolidation of these powders and demonstrate the potential for highly-reinforced, high-strength aluminum alloys to be used in applications requiring complex geometries, short lead times, or low part numbers.
9:40 AM
Laser-Powder Bed Fusion Processing Effects on Microstructural Texture in Nickel Superalloy: Frank Brinkley1; McKay Sperry1; Patxi Fernandez-Zelaia1; Christopher Ledford1; Michael Kirka1; 1Oak Ridge National Laboratory
Nickel superalloys are extensively used in aerospace and other applications requiring high temperature oxidation resistance and creep performance. Additive manufacturing processes such as laser powder bed fusion (L-PBF) offer unique capabilities to control the microstructure of nickel superalloys such as Inconel 625 (IN625). By varying the laser power, laser speed, and hatch spacing of the scan paths, the microstructure can be varied from equiaxed to elongated grains. This microstructural variation has been shown previously to be primarily driven by the solidification front dictated by the melt pool geometry and heat flow direction. Because component microstructure directly impacts the mechanical response, controllable microstructure can enable tailored mechanical properties based on component application. A methodology for varying crystallographic texture in IN625 produced via L-PBF by varying process parameters is demonstrated.
10:00 AM
Machine-Learning Assisted Prediction of Surface Roughness in Powder Bed Fusion Process with Inconel Super Alloy: Santosh Rauniyar1; Mathew Farias1; Ben Xu1; 1University of Houston
Controlling surface roughness is often a consideration when optimizing the powder bed fusion process for specific applications. Several factors and printing parameters contribute to the surface profiles, with laser power and scan speed being among the most influential. This paper presents an investigation into the prediction capability of machine learning algorithm to estimate the surface roughness profiles. Parts are printed by varying power and scan speed on five different levels using a design of experiments approach. Surface roughness data is acquired on the side surfaces of the as-built parts using a laser confocal microscope. The collected profile data is transformed using multiple feature extraction techniques and is then utilized to train a Neural Network. It is used to classify multiple line profiles labeled according to the parameter variation. The trained neural network demonstrates high accuracy in classifying line profiles to their associated laser parameters when tested with the new data.
10:20 AM Break
10:40 AM
Melt Track Formation Process with a Constant Linear Energy Density in Laser Powder Bed Fusion Revealed by In-situ X-Ray Imaging and Temperature Measurement: Yuki Wakai1; Naoki Seto2; Naoko Sato2; Yuta Kushiya1; Shinsuke Suzuki1; 1Waseda University; 2National Institute of Advanced Industrial Science and Technology
An understanding of a melting process during laser powder bed fusion is crucial for fabricating parts without support structures. However, the melting process in the powder bed remains unclear. This study aims to investigate the effects of laser parameters on a melt track formation in the powder bed via real-time monitoring methods. A 10 mm depth layer of pure Ti powder was irradiated by a laser under different laser power and scanning velocity with a constant linear energy density (10 J/mm). The X-ray imaging revealed that the spherical melt pool, which was formed under the laser irradiation point, moved in the opposite direction to the laser scanunder all laser conditions. However, the melt track shape tended to become discontinuous with increasing laser power and scanning velocity. The results obtained by the two-color pyrometer suggest that the discontinuous melt track was caused by spattering due to a rapidly temperature rise.
11:00 AM
Microstructure and Crack Propagation in IN718 Samples Fabricated by Laser Powder-Bed Fusion: Ishaan Sati1; Bharath Bhushan Ravichander1; Purna Sai Pavan Kalyan Nandigama1; Golden Kumar1; 1University of Texas at Dallas
This study explores the relationship between laser power levels and microstructures in Inconel 718 parts made via laser powder bed fusion, along with the impact of quasistatic loading on notched specimens. The other process parameters are kept constant to critically examine and isolate the impact of varying laser power. By varying laser power, it uncovers changes in melt pool geometry, density, porosity, and grain structure, affecting mechanical properties under load. An increase in laser power helps in eliminating defects, but a continued increase in its value could introduce defects which are detrimental. The formation of different grain structures due to a variation in the cooling rate plays an important role in the crack propagation that occurs in notched specimens under the application of a quasistatic load. The research emphasizes the importance of optimizing laser power while cautioning against uncontrolled increases due to potential adverse effects on part integrity and performance.
11:20 AM
Effect of Process Parameters on the Properties of IN718 Prepared by Laser Powder-Bed Fusion: Purna Sai Pavan Kalyan Nandigama1; Bharath Bhushan Ravichander1; Golden Kumar1; 1University of Texas at Dallas
Inconel 718 (IN718) is a nickel-based superalloy used in aerospace and oil industry due to its superior high temperature mechanical properties , corrosion resistance, fatigue resistance, and weldability.. Laser powder-bed fusion (LPBF), a rapidly growing additive manufacturing technique is capable of fabricating complex metals parts with controllable properties. The properties of metal parts produced via LPBF are highly sensitive to the process parameters due to complex thermo-fluid interactions. Hence, optimizing the process parameters is crucial to enhance the reliability of LPBFd parts. This study investigates the effect of laser power and scan speed on the microstructure and mechanical properties of as-built IN718. Optimal processing conditions are identified for achieving high density, microhardness, ultimate tensile strength, and ductility.
11:40 AM
Shape Memory Alloy Enabled Interlocking Metasurfaces by L-PBF: Abdelrahman Elsayed1; 1Texas A&M
This study examines the use of the shape memory effect in NiTi shape memory alloys (SMAs) for Interlocking Metasurfaces (ILM). Two designs of surface feature arrays were created using NiTi powders and laser powder bed fusion additive manufacturing (AM). These designs were tested to assess their locking force under thermal cycling. The results indicate that the interlocks exhibit high locking force, complete shape recovery, and cyclic stability. Finite Element Analysis (FEA) was employed to predict strain values during deformation and to guide the design process. FEA results forecast the maximum transformation strain during deformation, which can be recovered by heating, enabling the material to revert to its original shape. The findings suggest that NiTi SMAs can be utilized for designing and fabricating complex, high-force interlocking metasurfaces, facilitated by AM, which can be locked in place by heating and reused through the shape memory effect.
12:00 PM
Influence of Novel Space Filling PBF-LB Scanning Strategies on Part Distortion and Density: Maximilian Frey1; Max Frankenhauser1; Volker Schulze1; Frederik Zanger1; 1Karlsruhe Institute of Technology
Additive Manufacturing, especially Powder Bed Fusion – Laser Beam (PBF-LB), is known for its ability to create intricate designs with high precision. Yet, residual stresses remain a challenge, causing distortion. Novel laser paths, including various spiral and space-filling curves such as Hilbert, Gosper, and Peano, have been investigated. They were compared with standard stripe strategies. Parameters such as scan length and hatch distance are varied while maintaining energy density constant. Cantilever beams were used to measure distortion and density. Fractal strategies show minimal distortion with slight density loss. Spiral paths lead to a minimized porosity but show an increased distortion. Segmenting paths reduce distortion across all strategies. The orientation of the cantilever relative to the gas flow affects the distortion extent. Gosper and Hilbert curves reduce distortion with slight density reduction, while spiral paths minimize porosity but increase distortion. Segmenting paths effectively reduce distortion without density loss in all strategies.