Thermally Sprayed Abradable Coatings in Steam Turbines: Design Integration and Functionality Testing

Abstract

The concept of thermally sprayed abradable sealing technology has successfully been used in aero engines and industrial gas turbines for several decades now. More recently efforts were undertaken to implement the concept of seal coatings in steam turbine designs. As these typically use labyrinth type sealing, the application and test methods for sprayed seals applied to improve efficiency and reduce emissions need to be tailored to this particular seal configuration. This paper reviews how steam turbines can benefit from abradable coating technology and how it can be implemented into existing labyrinth seal designs for various seal locations in a steam turbine. A detailed review of high temperature rig abradability testing capabilities for labyrinth seal layouts using abradable coatings will be provided. Coating materials and their performance in a high temperature steam environment at 650 °C ( 1200 °F ) will be discussed. The application of coatings to various steam turbine components including large casings will be reviewed.