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 production reliability has been a concern.  This paper will look at ways reliability of performance has been improved through various designs of experiments and critical quality control procedures.  Some of the critical plasma parameters investigated in order to optimize coating microstructure and performance has been primary gas flow, secondary gas flow and powder.  Based on this information and better understanding and control of quality standards; hardness measurement techniques, metallographic polishing procedures and tensile testing the designer is in a better position to create an improved specifications for coating applicators.  Improved understandings of process parameters that better define the cause and effect on properties like hardness have a critical effect on engine abradability and erosion and thermal cyclic performance.