Microstructure and Material Properties of Alloy 718/713LC Joints Using Orbital Friction Welding

Abstract

This work demonstrates on flat test specimens that orbital friction welding is a suitable process to join a typical disk alloy 718 and a typical blade alloy 713LC. The capability to join nickel-based blades on disks enables the manufacture of blisks instead of the typically used bladed disks. Blisks have the potential to save weight within an aero engine. Orbital friction welding is an alternative process to linear friction welding to enable blade and disk joints. The advantage of orbital friction welding is that the movement is homogenous and the amplitude (or eccentricity) is smaller compared to linear friction welding. This allows joints in areas which are geometrically challenging and impossible to join for linear friction welding. Due to the solid state joining process, there is basically no material mixing within the weld, but within both alloys, recrystallization can be seen near the weld line. The result is a fine-grained microstructure within both alloys adjacent to the bond line. While this means only a small microstructural change for alloy 718, it is a major microstructural change for the cast coarse grain alloy 713LC. Consequently, the mechanical properties are changed compared to the base material due to the friction welding process. The microstructural changes of orbital friction welding and their influence on the material properties are presented within this work.