In-process thermal imaging of the electron beam freeform fabrication process

Abstract

Researchers at NASA Langley Research Center have been developing the Electron Beam Freeform Fabrication (EBF 3 ) metal additive manufacturing process for the past 15 years. In this process, an electron beam is used as a heat source to create a small molten pool on a substrate into which wire is fed. The electron beam and wire feed assembly are translated with respect to the substrate to follow a predetermined tool path. This process is repeated in a layer-wise fashion to fabricate metal structural components. In-process imaging has been integrated into the EBF 3 system using a near-infrared (NIR) camera. The images are processed to provide thermal and spatial measurements that have been incorporated into a closedloop control system to maintain consistent thermal conditions throughout the build. Other information in the thermal images is being used to assess quality in real time by detecting flaws in prior layers of the deposit. NIR camera incorporation into the system has improved the consistency of the deposited material and provides the potential for realtime flaw detection which, ultimately, could lead to the manufacture of better, more reliable components using this additive manufacturing process.

Fusion‐Based Additive Manufacturing for Processing Aluminum Alloys: State‐of‐the‐Art and Challenges

“…Al–Cu (2xxx series) alloys have been fabricated successfully by LBM of pre‐alloyed powders, in spite of a certain tendency of these alloys for solidification cracking due to the segregation of Cu‐rich compounds during solidification . AA2219 and AA2139 have been processed by wire‐feed EBM . Similarly to observations on Al–Si alloys, the ultra‐fast thermal cycles involved in LBM resulted in strongly refined and out‐of‐equilibrium microstructures …”

“…Wire‐based Electron Beam Melting (EBM) of Al parts has known an early start when compared with processes relying on a laser as heat source . EBM appeared particularly promising for the manufacturing of highly reflective metals such as Al.…”

“…EBM appeared particularly promising for the manufacturing of highly reflective metals such as Al. Wire‐based EBM was used successfully to make sound components from Al–Cu alloys (AA2024 and AA2219) or from Al–Sc alloys . Similarly to what happens in laser‐based processes, the extremely high cooling rates involved in EBM result in strongly refined out‐of‐equilibrium microstructures, giving rise to high hardness and strength .…”

Numerical Modelling of Heat Transfer and Material Flow During Wire-Based Electron Beam Additive Manufacturing

“…В настоящее время практически нерешенной задачей остается контроль режима переноса металла, который подвержен влиянию многих факторов, и прежде всего связан с непостоянством условий теплопередачи в системе "источник нагрева -подслой". Изучение процесса тепломассопереноса может осуществляться экспериментальными методами, что требует использования дорогостоящего тепловизионного оборудования [11,12]. Однако даже в случае его использования исследователи получают лишь косвенную информацию -распределение температуры по поверхности валика и проволоки.…”

Integration of Deformation Processing with Additive Manufacture of Ti‐6A1‐4V Components for Improved β Grain Structure and Texture

“…There is potential for the aerospace industry to greatly benefit from Additive Manufacture (AM) as it allows the near-net-shape manufacture of components [1][2][3][4][5][6][7] and provides more design freedom than traditional manufacturing, which can facilitate substantial weight savings through better design optimisation [1]. Ti-6Al-4V is one of the most widely used titanium aerospace alloys due to its high specific properties [8].…”