Repair and Life Extension of Titanium Alloy Fan Blades in Aircraft Gas Turbines

Commercial and military aircraft gas turbine fan blades can suffer various types of damage in service, such as foreign object damage (FOD), high strain low cycle fatigue (LCF), wear and fretting fatigue. In addition, cracks initiated by one or more of these types of damage may propagate by a high cycle fatigue (HCF) mechanism. The component may therefore be life limited by the dominant failure mechanism.In this paper, a new, comprehensive scheme for economical refurbishment and qualification of service damaged titanium alloy fan blades is described, along with a critical review of the merits and demerits of existing repair schemes. The metallurgical and process variables to be considered in the repair of FOD, LCF life extension, wear and fretting fatigue life improvement are considered in detail with practical examples derived from experience.A complete qualification testing program including metallography, non-destructive inspection and mechanical property testing, for the refurbished component is outlined.Copyright © 1989 by ASME