In-situ cladding of leading edge of lp turbine blades using fibre delivered diode laser

Abstract

Reliable and efficient power generation is a major global issue due to both political and environmental concerns. Nevertheless many critical components, particularly the blades of the low pressure (LP) side of power generating steam turbines, are subjected to failure due to severe erosion at the leading edges. Since taking machines off-line for maintenance and removal of damaged blade for repair is extremely expensive, increasing the service life of these critical components offers significant economic and political benefits. Conventional techniques to increase service life include brazing of an erosion shield at the leading edge of the turbine blades, open arc hardfacing, and cladding with erosion resistant materials using gas tungsten, manual metal or plasma transferred arc welding. The martensitic stainless steels used to produce blades are highly susceptible to cracking and metallurgical change when subjected to heating and cooling. The repair of damaged blades with the above techniques is also subjected to similar difficulties. We have investigated the potential of laser cladding [1-3] to deposit a high quality and erosion resistant protection shield on the leading edge of LP blades. Laser cladding offers unique advantages over the conventional techniques. The project to-date has demonstrated the feasibility of in-situ repair of turbine blades in trials conducted at a power station using a fibre delivered diode laser and a robot.