Reconditioning Technologies for Film Cooled Single Crystal Turbine Blading

Increased availability, reliability, and performance combined with reduced maintenance costs are key factors for the success of gas turbine users. This paper focuses on the reconditioning of film cooled single crystal (SX) components used in the GT24 and GT26 fleet and the latest enabling technologies. The general reconditioning strategy is based on a thorough analysis of the accumulated field experience with SX parts and a controlled, stepwise introduction of new techniques. Reconditioning processes have been developed for different damage scenarios for components. This would include the most technically challenging SX “heavy” scope reconditioning. This paper gives an overview about the reconditioning sequence for SX components and some of its key process steps. As an example, the crack braze repair process is described in detail and several novel SX welding techniques for crack repairs and blade tip and temperature controlled leading edge wall thickness restoration are shown. This covers different processes such as tungsten inert gas (TIG) welding or laser metal forming (LMF) of SX components. During the last few years, highly automated production solutions and innovative production tools have been implemented, which enable high capacity and consistently high quality of reconditioning. After their successful validation and a limited phase of monitored production, these techniques are applied on rotating and stationary SX turbine parts. Validation criteria and the experience gained during the first years of commercial production and operation in the field will be presented.