Turbine blades
A new Group Sponsored Project has recently been launched for the power generation and aero-engine sectors. It focuses on the repair of gas turbine blades and nozzle guide vanes. These parts are considered extremely difficult to repair by conventional processes, such as manual TIG welding and brazing, because of the susceptibility of the creep resistant alloys to HAZ and weld metal cracking. This problem has been compounded by the increasing use of directionally solidified and single crystal alloys, where their creep properties are undermined by the grain growth encouraged by fusion repair processes.
The savings to be made from repair range from £50 000 for a set of equi-axed blades in a small aero engine gas turbine to several million pounds for a set of single crystal blades in a large power generation gas turbine. The main emphasis will be on repair by Nd:YAG laser and mechanised TIG welding and will focus on:
- Production of high strength repairs to IN738LC and single crystal CMSX4 components with matching or alternative consumable
- Determination of limits to blade repair (eg maximum crack depth)
- Validation of repairs by low cycle fatigue and creep testing
- Automation of turbine blade repair procedures
Partners are invited to supply used turbine blades for repair feasibility studies, where the focus will be on those regions commonly damaged in service such as blade tips, shroud seals, shroud edges, shroud/airfoil intersections and airfoil leading edges.
For further information contact David Harvey or Geoff Melton. E-mail: dave.harvey@twi.co.uk or geoff.melton@twi.co.uk.
