Optimization of an Aluminum Silicon-hexagonal Boron Nitride Abradable Coating for Improved Reliability and Performance

Aluminum silicon based abradables have been used for many years in Aerospace high pressure compressor applications.  These coating systems typical use nickel aluminum bond coat and cut against titanium blades for temperature up to 450C. Although technically successful compared to other coatings systems and production reliability has been improved to be in excess of 98% in terms of conformance to the defined engineering standard, further improvements in system performance are needed to minimize engine life-cycle costs. This paper will review the procedures defined to further improve reliability of the coating system, these include, design of experiments and definition of critical to quality control procedures, and how these have resulted in improved understanding of process parameters that better define the relationship between coating attributes such as hardness, erosion and thermal cycling performance, and how this can be linked to the functionality in the engine environment.