Electron-Beam Additive Manufacturing Process Control for Titanium Alloys

Machining of titanium parts from wrought stock costs as much as $1000 to $1500 per pound of finished component and has material lead times up to one year.   Electron beam deposition, or e-BAM, seeks to dramatically reduce these costs and lead times.   However, this is not possible without IPQA in-process quality assurance that monitors and controls key process variables during deposition. Our detailed technical cost model shows that without IPQA, eBAM  is at $750 per pound, with IPQA this drops to below $600, and with optimized post process operations, $300 per pound is achievable.  We propose both imaging and non-imaging sensors resulting in a constant weld pool volume eBAM process.   We will use a vision-based system looking through the electron beam optical column, and a non-imaging sensor that channels light from the weld pool to a photodiode array.   We also utilize a real-time thermal inverse model that links local weld pool measurements to global process parameters like travel speed, wire feed, and beam power resulting in a models-based control scheme.  Lastly, we have assembled all the deposition and post-deposition disciplines required to achieve optimized eBAM costs of $300 per pound in a Phase II demo. BENEFITS: By achieving an eBAM cost as low as $300 per pound, dramatic improvements will be achieved in aircraft and aeroengine prototyping, rapid product development, and even LRIP low rate initial production.   Also the associated lead times for flight hardware will drop from over one year to less than three months for new designs. The takt time for parts less than 40lbs total deposit weight (the part itself could be considerably heavier on account of large plate stock onto which deposits are made) using the optimized eBAM process described in this proposal is approximately 6-7 hours, which means it is possible to get one part per day, or an LRIP production rate for a single eBAM work cell without any redundant process equipment of 20 parts per month ( 40 per month if two shift operation) assuming a 5-day per week, 8-hour per day shift.   The logistical implications for both OEM and spare parts are tremendously favourable.    It is anticipated that such tremendous cost, lead time and productivity benefits will also accrue to other titanium parts for other defence applications as well as commercial aviation, or to any application that utilizes large, high quality titanium parts.  Also, the same methodology could be adapted to steel, monel and aluminium bronze parts, thereby similarly revolutionizing the supply chain for critical naval spares.