Novel Ceramic Abradable Coatings With Enhanced Performance

Abstract

Abradable coatings are employed in modern gas turbine engines to minimize clearance and reduce over-tip leakage by allowing blade tips to cut into the coating. While such clearance control coatings have been used in the compressor modules of jet engines and stationary gas turbines for many years, their use in the High Pressure (HP) section of turbine modules is relatively new. Because of the high temperatures encountered there, ceramic materials must be used to provide a durable seal. In this paper the performance of two novel ceramic abradable seal coatings is reviewed and compared to a baseline system. Emphasis is placed on the resistance to thermal shock and erosion. The abradability of coatings by hard tipped blades is reviewed using a wear map consisting of five distinctly different rub test conditions. Among the coatings considered, an APS sprayed dysprosia stabilized zirconia ceramic abradable offers a potentially superior combination of thermal shock resistance, abradability and erosion resistance for high temperature turbine seal applications.