Linear Friction

Linear friction welding joins parts by oscillating one component under force to create a solid-state bond with minimal HAZ and high joint strength.

Overview

Linear friction welding (LFW) is a solid-state process where two parts are pressed together while one oscillates in a straight line. Frictional heating plasticizes the interface, flash is expelled, and the parts forge into a high-strength joint without melting. It produces repeatable welds with a small heat-affected zone and low distortion compared with fusion welding.

Choose LFW for high-value alloys and critical joints where strength, fatigue performance, and cleanliness matter—especially when joining dissimilar or hard-to-weld materials. It works best on parts with flat, accessible faying surfaces and enough cross-section to carry axial forging loads.

Tradeoffs: specialized equipment and fixturing drive setup cost; joint area and part envelope are limited by machine stroke/force; flash must be managed and often machined off; tight fit-up and robust clamping are mandatory. Post-weld heat treat may be required for some alloys to restore properties.

Common Materials

  • Titanium Ti-6Al-4V
  • Inconel 718
  • Aluminum 7075
  • Stainless Steel 17-4PH
  • Low Alloy Steel 4140

Tolerances

±0.003"

Applications

  • Blisks (integrally bladed rotors)
  • Compressor blade to disk joints
  • Titanium structural brackets
  • Tool steel die or mold repairs
  • Bimetallic drive shafts
  • Landing gear subcomponents

When to Choose Linear Friction

Linear friction welding fits medium-volume to production runs where the same joint is repeated and joint performance is critical. It’s a strong choice for flat-interface joints in high-strength alloys where low distortion and minimal HAZ matter. Plan on machining allowance for flash and on fixtures that can react high forging forces.

vs Rotary Friction

Choose linear friction when the joint can’t be axisymmetric or rotating (non-round parts, blade-to-disk style joints). It allows rectangular or complex planform interfaces, but requires more demanding fixturing and often higher equipment cost for large parts.

vs TIG Welding (GTAW)

Choose linear friction when you need near-parent-metal strength with minimal HAZ, low distortion, and no filler metal. It avoids solidification defects and reduces rework on heat-sensitive alloys, but it can’t reach deep, complex seam paths like manual/automated GTAW.

vs Electron Beam Welding (EBW)

Choose linear friction when you want a solid-state bond without vacuum chamber constraints and with lower sensitivity to joint contamination at the molten pool level. EBW handles deep, narrow welds in complex assemblies; LFW is better for repeatable, high-strength planar interfaces.

vs Brazing

Choose linear friction when joint strength and high-temperature capability must approach the base material and you can tolerate flash removal. Brazing is better for thin sections and complex capillary joints; LFW is better for structural load paths and fatigue performance.

Design Considerations

  • Design a flat, accessible faying surface with consistent contact area to stabilize heat generation and upset
  • Provide machining stock for flash on all sides of the weld line and define which surfaces must remain undisturbed
  • Specify realistic fit-up and flatness at the interface; gaps and waviness reduce weld quality and repeatability
  • Include robust clamp lands or fixture datums near the joint to react axial force without part distortion
  • Avoid very thin sections adjacent to the weld; add local thickness or ribs to prevent buckling during forging
  • Call out post-weld heat treat and final machining sequence early; properties and distortion depend on the full process route