Joining error resulted in failure of an aircraft engine radial diffuser

Radial diffuser is fixed in the cold region of engine. It guides the air into axial diffusers with increased pressure and reduced velocity. Resistance welding and brazing process was used in the fabrication of radial diffuser.Failure analysis of the radial diffuser showed that it was failed due to fatigue. Problem started with erosion of brazing at leading edge of diffuser vane at lower side. It un-tied the leading edge up to the welded region. In this condition vanes become one side supported cantilever. They were experiencing a pressure gradient on both sides. A lot of defects were observed in the welding region. These become the crack(s) initiation sites which propagated into the vanes under fatigue mechanism and finally fractured.