Current and Next-Generation Titanium Blade Compatible Compressor Abradable Coatings

Compressor abradables that will come in operational contact with bare, un-tipped titanium alloy rotor blades over a wide range of incursion conditions, require excellent cuttability in order to avoid blade tip damage by wear and over-heating. This is more easily achieved for low temperature systems that can make use of low shear strength aluminium matrices than for compressor abradables operating closer to the maximum allowable temperature of advanced titanium alloy blade materials, as these rotor path linings will have to incorporate higher temperature resistant Ni and Co alloy matrices. To that end the availability of abradable coatings capable of operating at up to 550 °C while showing little ageing effects and excellent abradability over their entire service life can influence the compressor blade material selection and therefore compressor weight and performance characteristics.

This paper provides an overview of titanium blade friendly compressor abradable concepts. A particular emphasis will be placed on in-service and next-generation coatings designed for use at and above the temperature capability of Ti blade rotor materials. Candidate coatings are screened for their main performance criteria: abradability, thermal cyclic resistance, solid particle erosion resistance and ageing behaviour.