GKN Aerospace and Pratt & Whitney have expanded their additive manufacturing collaboration to include a large structural case for the F135 engine used by the F-35 combat aircraft.
Under a technology development agreement supported by the Norwegian Defence Materiel Agency, work will be led from GKN Aerospace’s Kongsberg operation using wire-based laser directed energy deposition. A full-scale demonstrator is planned for 2027, followed by a targeted certified production component during 2028.
The finished case is intended to remain interchangeable with the existing engine structure, allowing it to enter the established design without extensive changes to surrounding hardware or maintenance procedures. Achieving that compatibility requires the additive component to reproduce the geometry, interfaces, material behaviour, and service life of the current part.
Wire-based directed energy deposition feeds metal wire into a melt pool created by a laser, building the structure through successive deposited paths. Heat treatment, machining, inspection, and finishing then bring the near-net-shape component to the dimensions and surface condition required by the engine.
Large aerospace structures are commonly machined from forgings or billets that may contain considerably more metal than the finished part. Depositing material nearer to the final geometry can reduce waste and machining time while creating another route for parts constrained by limited forging or casting capacity.
An engine case carries substantial mechanical responsibility, maintaining alignment, supporting interfaces, transmitting loads, and operating under vibration and changing temperature. The deposited material must therefore achieve controlled properties across a large volume rather than merely demonstrate that the required shape can be printed.
Wire chemistry, shielding gas, laser power, deposition rate, path sequence, interpass temperature, and cooling behaviour influence grain structure, residual stress, distortion, porosity, and fusion between layers. Process variation that appears minor during manufacture can affect fatigue performance after machining has removed the visible surface.
Certification requires a repeatable material process
The full-scale demonstrator will establish whether the geometry can be produced, but qualification must extend across machines, operators, wire batches, maintenance cycles, and production periods. Repeatability is particularly demanding where a large build may run for many hours and thermal conditions change as the structure grows.
Process monitoring can record melt-pool behaviour, temperature, energy input, deposited geometry, and machine condition throughout the build. Such data may support the quality case, although each signal must be correlated with material performance and clear acceptance limits before monitoring can replace or reduce conventional inspection.
Post-processing remains central to the route. Heat treatment is used to control microstructure and relieve stress, while critical interfaces require precision machining. Large cases need careful fixturing because removing material can release residual stress and alter the final geometry.
Non-destructive examination must identify defects capable of affecting fatigue life, containment, or structural integrity. Ultrasonic testing, radiography, surface inspection, dimensional measurement, and test coupons may all form part of the qualification plan, depending on geometry and the accessibility of deposited regions.
Building a larger integrated structure can reduce part count and remove joints, but it also concentrates value within each component. A defect discovered near the end of manufacture can represent substantial machine time and material, increasing the importance of early detection and validated repair limits.
Pratt & Whitney is also applying additive manufacture to more highly consolidated propulsion systems. Its TJ150 compact engine demonstrator reduced more than 50 hot-section parts to a small number of printed assemblies, illustrating how the technology can alter assembly as well as individual component manufacture.
The F135 case addresses a different production requirement because it must enter a mature engine programme with an established fleet, support system, and configuration baseline. Compatibility, field maintenance, and production assurance carry as much weight as the potential reduction in material waste.
Defence propulsion supply chains are under pressure to increase output while supporting engines already in service. Forgings, castings, specialist alloys, heat treatment, precision machining, coatings, and inspection can each become constraints, particularly where suppliers also serve civil aerospace programmes.
A qualified additive route could provide additional capacity and reduce reliance on one upstream manufacturing process. It would still require specialist material, deposition machines, heat treatment, machining, inspection, and trained personnel, but those resources can be distributed differently from a conventional forging chain.
Wire feedstock is generally easier to handle at large scale than the fine powders used in powder-bed fusion, while directed energy deposition can build structures exceeding the chamber size of many powder systems. The trade-off is a rougher surface and lower deposited precision, leaving more work for machining and finishing.
Production economics will depend on deposition rate, wire use, machine availability, post-processing, inspection, and yield. Material savings alone may not justify the route if long build cycles or high rejection rates offset the reduction in conventional machining.
Norwegian support connects the technical programme with national industrial participation, building advanced engine-manufacturing capability at Kongsberg while contributing a component route for a large international aircraft fleet.
The 2027 demonstrator will provide the first full-scale evidence, but the 2028 certification objective requires a much broader manufacturing case. Material behaviour, machine control, inspection, heat treatment, machining, and production records must combine into a process capable of supplying interchangeable engine hardware repeatedly.
