Repair Process Technology Development and Experience for W501F Row 1 Hot Gas Path Blades

Volatile market dynamics in the electrical power generation field continues to force power companies to identify prudent material cost reductions opportunities in their Operations and Maintenance (O&M) business. Today, there is an industry-recognized need for advanced hot gas path component repair and reconditioning capability for operators of F-Class gas turbines that can be highly cost effective with short cycle times. The SGT6-5000F (W501FD) engine, an “F” class machine has been in operation for more than a decade now. Of importance to operators/users and owners of this gas turbine engine is the ability to recondition the turbine “hot-end section” components, in order to support maintenance requirements. The first 2 rows of blades are unshrouded; whereas the last 2 rows are shrouded. The row 1 blades show severe degradation and thus repair of this component has been a focus point for PSM. The technical objective is to develop repair schemes for the row 1 blades since this component (other than the Transition Piece (TP)) has the highest frequency of replacement, plus is the highest replacement cost per component. Special processes have been developed for these components repairs, including but not limited to: a) Acid stripping of the coating; b) Machining off of the original brazed tip cap plates; c) High frequency gas tungsten arc welding and vacuum diffusion braze repair of platform cracks; d) High frequency gas tungsten arc weld attachment or laser welding of new tip cap plates; e) Laser metal forming/cladding of new squealer tips; f) Rejuvenation heat treatment; g) Application of superior MCrAlY and TBC coating to that originally applied. This technical paper describes the repair process development and implementation of the different stages of the repair schemes, and shows metallurgical and mechanical characteristics of the repaired regions of the component.