ELECTRON BEAM DEPOSITION

Electron beam freeform fabrication (EBF) is an emerging cross-cutting technology for producing structural metal parts. The process can be used to build a complex, unitized part in a layer-additive fashion, although the more immediate payoff is for use as a manufacturing process for adding details to components fabricated from simplified castings and forgings or plate products. Figure 1 shows a schematic of the primary elements of an EBF system. EBF employs a high power electron beam in a vacuum environment (1 ´ 10-4 torr or lower).

Wire feedstock is used due to difficulties feeding powder in a vacuum since the carrier gas used to assist powder delivery will be ionized in the electron beam. Operation in a vacuum ensures a clean process environment and eliminates the need for a consumable shield gas as is typically used in laser deposition systems. The EBF process is nearly 100% efficient in feedstock consumption and approaches 95% efficiency in power usage. The electron beam couples well with any electrically conductive material, including highly reflective alloys, such as aluminium and copper. A variety of weldable alloys can be processed using EBF; further development is required to determine if non-weldable alloys cam also be deposited. Demonstrated deposition rates for EBF are 330 to 2500 cm/hr (20 to 150 in3/hr), with lower resolution in the ability to build fine details. Experiments are planned with the fine diameter wires to attempt to construct fine details and large diameter wires to increase deposition rate, process efficiency, and material compatibility for insertion into the production environment.