Binder jetting additive manufacturing is an emerging technology with capability of processing a wide range of commercial materials, including metals and ceramics (316 SS, 420 SS, Inconel 625, Iron, Silica). In this project, aluminum oxide (Al 2 O 3) powder was used for part fabrication. Various build parameters (e.g. layer thickness, saturation, particle size) were modified and different sintering profiles were investigated to achieve nearly full-density parts (~96%). The material's microstructure and physical properties were characterized. Full XRD, compression testing, and dielectric testing were conducted on all parts. Sintered alumina parts were achieved with an average compressive strength of 131.86MPa(16 hours sintering profile) and a dielectric constant of 9.47 to 5.65 forafrequencyrangeof 20Hz to 1MHz. The complexityoffered by additive processing aluminum oxide can be extended to the manufacturing of high value energy and environmental components for environmental systems (e.g. filters and membranes) or biomedical implants with integrated reticulated structures for improved osseointegration.
Joining of dissimilar metals using high energy-density beams such as lasers and electron beams offer several advantages including precision, narrow fusion zones, and narrow heat affected zones (HAZ) that consequently result in reduced part distortion when compared to traditional joining processes. When high energy-density beams are combined with the design freedom offered by additive manufacturing (AM), or a layer-by-layer part fabrication process, it becomes possible to manufacture complex multi-material parts with improved joint characteristics resulting from controlled process parameters. Complex multi-material parts can be achieved that have tremendous impact on applications ranging from nuclear power plant components to repair applications. This research explores the feasibility of joining Inconel 718 with 316L Stainless Steel, and vice versa, by utilizing electron beam melting (EBM) additive manufacturing, a class of powder bed fusion technology. The use of this process can help avoid the use of filler materials, provides an evacuated processing environment resulting in limited contamination of oxides and nitrides, and can provide a high quality metallurgical joint while minimizing the thermal damage to surrounding material. Multi-material components were fabricated and the joint interfaces were characterized. Assessments of the interfaces revealed minimized thermal effects from the process and finer weld joints.
Energy system components with embedded sensors, or smart parts, can be a pathway in obtaining real-time system performance feedback and in situ monitoring during operation. Traditional surface contact or cavity placed sensors increase the possibility of disturbing the normal operation of energy systems due to changes in part design required for sensor placement. The fabrication of smart parts using additive manufacturing (AM) technology can allow the flexibility of embedding a sensor within a structure without compromising the structure and/or functionality. The embedding of a sensor within a desired location allows an end user the ability to monitor specific critical regions that are of interests such as high temperature and pressure (e.g. combustor inlet conditions that can reach up to 810K and 2760kPa). In addition, the nonintrusive placement of the sensor within a part's body can increase the sensor's life span by isolating the sensor from the aforementioned harsh operating environments. This paper focuses on the fabrication of smart parts using electron beam melting (EBM) AM technology as well as the characterization of the sensor's functionality. The development of a "stop and go" process was explored that comprised of pausing a part's fabrication process to allow the placement of piezoelectric ceramic material into pre-designed cavities within a part's body, and resuming the process to complete the final product. A compression test was performed on the smart parts fabricated using EBM to demonstrate the sensor's capability of sensing external forces. A maximum sensing voltage response of approximately 3V was detected with a maximum pressure not exceeding 40MPa. The sensor responses showed good agreement with the applied force in four different frequency conditions (i.e., 10Hz, 15Hz, 20Hz, and 25Hz). This research work demonstrates the feasibility of fabricating smart parts with embedded sensors without the need of post-processing (e.g., CNC machining and polishing). In addition, the sensing capability of monitoring a component's performance has been validated, leading to the possibility of fabricating other smart parts that could impact industries such as energy, aerospace, automotive, and biomedical industries for applications like air/fuel pre-mixing, pressure tubes, and turbine blades.
Quality assurance is an important topic for additive manufacturing (AM) and often seen as a requirement for the transition and adoption of the technology toward fabrication of end use applications. As AM technologies are used for production, it is necessary to ensure high quality, repeatable, and reproducible components are manufactured. Various nondestructive examination techniques have been used to evaluate AM-fabricated parts to determine part quality post-fabrication (e.g. scanning and/or microstructural characterization). In situ monitoring methods have been developed for AM technologies to enable defect detection and have potential to be used for in situ monitoring and correction of fabrication anomalies (e.g. undesired temperature gradients and porosity). In this research, defects (e.g. pores) were seeded into parts fabricated using the powder bed fusion AM process, electron beam melting, and monitored using in situ infrared (IR) thermography. Results from layerwise thermography were compared with results obtained using computer tomography (CT) scanning techniques. Although the measured geometry of the seeded defects between IR thermography and CT was substantially different (area difference of ∼60%), the thermographs did provide a good indication of defects present within a fabricated part. Furthermore, defect correction methods were evaluated including post-processing methods such as hot isostatic pressing as well as in situ correction methods such as layer re-melting. Re-melting a porous layer successfully corrected defects and demonstrates a potential method for in situ defect correction if implemented in future systems equipped with automatic feedback control of powder bed fusion processes.
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