Abstract
Linear Friction Welding (LFW) is a solid-state joining process very well adapted to titanium alloys, producing high integrity joints with fine grain, hot-forged microstructure and narrow heat affected zone. The first industrial application of this process was found in aircraft engines, for the manufacturing of “blisks” (“bladed disks”): linear friction welding the blades onto a disk provides economic savings and reduces the manufacturing time, compared to machining the whole blisk from solid. While the diffusion of LFW process in the blisk manufacturing market is still at the early stages and have promising growth potential, the process is now being developed for aircraft structures such as clips, brackets, hinges, fittings, and larger parts like seat rails, wing ribs, lintels and fuselage frames. The LFW process allows not only to manufacture a given part at a lower cost, it also open new part design possibilities, that were not available with traditional manufacturing processes. The manufacturing process of Ti-6Al-4V structural and engine parts by LFW is explained, highlighting advantages, limitations and part design best practices. Several LFW candidate parts are introduced and evaluated through feasibility, mass savings, post weld operations and overall cost savings.
Highlights
Linear Friction Welding (LFW) is a solid-state joining process involving the use of a linear reciprocating movement of two pieces under high contact pressure
LFW is a low temperature welding It means, there is no melting of the parent material
The combination of low temperature and short cycle time leads to low heat input, so small Heat Affected Zone (HAZ)
Summary
Linear Friction Welding (LFW) is a solid-state joining process involving the use of a linear reciprocating movement of two pieces under high contact pressure. The frictional heat locally softens the material, which is expelled from the interface due to axial load. A forge phase ensues from the friction phase: oscillation motion is stopped; the two components are brought into perfect alignment and the welding force is maintained or increased to consolidate the joint. The pressure is applied, and the oscillation motion starts. Pressure and motion are still applied, and the material is expelled. The process is control through four main parameters: Frequency of oscillation (30 Hz to 60 Hz) Amplitude (±1 to ±3 mm) Forge pressure (70 to 110 MPa) Upset (1 to 3 mm) The values in parenthesis are typical values forTi-6Al-4V.
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