Linear friction welding method

#The present invention relates to a method of linear friction welding a rotor blade to a disk.

#Friction welding is the process for welding together two bodies or workpieces by converting mechanical energy to heat energy by the friction between the engaging weld surfaces of the two workpieces. In rotary friction welding, the process involves effecting relative rotation between the two workpieces while the weld surfaces remain in engagement with each other. In linear friction welding, the process involves effecting relative lateral oscillation between the two workpieces while the weld surfaces remain in engagement with each other.

#Compressors and turbines of gas turbine engines such as those used in aero engines typically include a plurality of rotor and stator vane assemblies. The rotor assemblies are designed to impart work into gases passing through the compressor and extract work from the gases passing through the turbine. The stator vane assemblies help to direct the working gases entering or exiting the rotor assemblies and thereby increase efficiency of the engine.

#Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

#FIG. 1 is a perspective view of part of an integrally bladed rotor assembly;

#FIG. 2 shows schematically a production blade mounted at a blade tooling of a linear friction welding machine in a suitable alignment with a rim of a disk to start linear friction welding;

#Referring to FIG. 1, there is illustrated a part of an integrally bladed rotor assembly 10 which may be used in the compressor or turbine of an aero engine. The rotor assembly 10 includes a plurality of blades 12 attached to a rim of a disk 14 so as to extend radially outwardly therefrom. The blades 12 are typically of a titanium, nickel or steel alloy (a titanium 6-4 alloy commonly being used) and are attached to the rim by LFW. This can involve holding the disk stationary while a blade (generally in an un-machined/unfinished state) is oscillated against the rim under a radial forge load. For example, the blade member may be oscillated axially or tangentially against the rim. The heat generated by the oscillation together with the radial load results in the material of the blade member and rim becoming viscoplastic. When the material subsequently cools, bonds are formed and a weld is created between the rim and the blade. During the LFW process, upset material (“flash”) is extruded from the sides of the joint. The blade is subsequently machined into shape, the material at the edges of the weld being removed.

#FIG. 2 shows schematically a production blade 12 in a suitable alignment with a rim of a disk 14 to start LFW. The blade has an aerofoil portion 16, a foot portion 18 from which the aerofoil portion extends radially outwardly, and a stub 20 of sacrificial material which projects radially inwardly from the foot portion. The disk has a corresponding stub 22 of sacrificial material which projects radially outwardly from its rim. The blade is mounted at a blade tooling 24 of a LFW machine, the blade tooling including a cassette 24a at the foot of the blade to which holds the blade and a forge block 24b radially outwardly of the cassette through which the radial forge load is transmitted. The machine has a further tooling (not shown) at which the disk is mounted.

#During the LFW process, which results in the consumption of the stubs 20, 22, the disk 14 is held stationary while the blade 12 is oscillated against it under the forge load. When the process is completed, the blade is thus welded to the disk at its foot portion 18. The disk rim and foot portion can then be machined and finished.