Laser cladding repair of lp steam turbine blades

The reliable, efficient and cost effective running of large steam powered electric generators is essential for the maintenance of our modern society. Erosive wear of blades as a result of droplet formation within the turbines is both endemic and costly. It results in the need for complex and expensive off-line repairs as well as unwanted downtime of power generation equipment. Furthermore, if the results of erosion are ignored there can be inefficient operation, reduced blade life and in extreme cases catastrophic failure can occur within the turbine. This paper presents the results of research into successful repairs to the outer leading edge of low pressure steam turbine blades. A high power fibre delivered diode laser was installed on site at the power station to laser clad a Stellite 6 coating to the eroded areas of the blades and so effect a repair. This required the construction of a compact co-axial laser cladding head capable of fitting within the restricted space that exists between the blades that were still attached to the rotor shaft. The blades themselves are constructed of martensitic stainless steel which is highly susceptible to cracking and metallurgical change when subjected to heating and cooling [1]. The cladding process has resulted in a crack free blade with minimal distortion.