Solid state joining of metals by linear friction welding: a literature review

Linear friction welding (LFW) is a solid state joining process in which a joint between two metals can be formed through the intimate contact of a plasticised layer at the interface of the adjoining specimens. This plasticised layer is created through a combination of frictional heating, which occurs as a result of pushing a stationary workpiece against one that is moving in a linear reciprocating manner, and applied force. The process is currently established as a niche technology for the fabrication of titanium alloy bladed disc (blisk) assemblies in aeroengines, and is being developed for nickel based superalloy assemblies. However, interest is growing in utilising the process in a wider range of applications that also employ non-aeroengine metallic materials. Therefore, it is the objective of this report to provide a broad view of the capabilities of the LFW process for joining metals. This review paper will cover relevant published work conducted to date on LFW. The basics of the process and the fundamental aspects of operating a LFW machine will first be described, followed by a description of the different materials that have been welded using the process. The review will then go on to describe the microstructural changes, including texture variations, and residual stresses that are produced as a result of the welding process.