Linear Friction Welding was discovered in the 1960's, but the complexity and precision of the required control system, as well as the huge hydraulic pressure and flow required, put it aside for decades.  Its principle is unqiue yet simple.  The parts to join are assembled in custom tooling, and when put in reciprocal linear oscillation under pressure, generate friction heat.  Their interface rises to the plasticisation temperature then yields.  A flash is then expulsed from the interface, at the rhythm of oscillation.  Once in final position, a forging force is applied as the now bonded part is cooling down.  This results in an integral atomic diffusion bond on the weld plane, of which the mechanical properties are only slightly modified.

This process results in minimal component distortion and high weld strength.  It also lends itself to
obtaining desirable microstructure in the weld, and in the heat affected zone.

Linear Friction Welding (LFW) is used when the benefits of friction welding are desired, but the geometries of the parts do not adhere to a conventional means of rotational friction welding.  LFW uses an oscillating motion rather than a rotating motion to generate the heat required for the weld.  LFW applies to a wide variety of part geometries, and is not limited by weld area or thickness.

Linear Friction Welding is finding use in diversified applications at a rapid rate.  The aerospace industry is the forerunner.  The most popular application is the fabrication or repair of integrated blades and disks (BLISK), also named integrally bladed rotors (IBR).  Other potential applications are in the automotive industry, gas and oil transmission pipelines, and the construction industry.  In general, any application where conventional welding has difficulty meeting your requirements should be considered as a potential opportunity for LFW.

Other objectives leading to LFW applications include:

• Reducing raw material cost and machining time by reducing the size of the casting or forging and
  attaching components where they are necessary (for example, attach a boss to a fan case or
  intermediate case).

• Reducing raw material cost and improving quality with bi-material applications, using the high cost
  material only where necessary.

• Suitable for quantities ranging from prototypes to high production with less than a 2 seconds
  weld time.