New High Temperature Titanium Compatible Abradable Seals

摘要

Abradable seals are used to control the over-tip leakage of gas between rotor blades and casings, and hence to increase compressor efficiency and decrease fuel consumption. Abradable seals allow the blade to cut a track into the abradable coating but this has to be achieved with minimum blade wear. The aircraft engine performance can be improved by decreasing the ratio of engine weight to take-off thrust. Replacing the heavier nickel based compressor blades with titanium alloys is one of the preferred ways. However, abradables satisfactory for rubbing against nickel superalloys may not be satisfactory against titanium based hardware. The seals generally used in the back end of the HP compressor represent an unacceptable fire risk when run against titanium blades, which means that manufacturers are limited to nickel blades with the associated weight penalty or they have to incorporate a very expensive blade tip treatment on the titanium blades. In response to this requirement, a new high temperature titanium compatible seal has been developed at Westaim Ambeon. The main goal of this paper is to describe and evaluate the new abradable seal, for use at temperatures up to 650℃, having good abradability and erosion resistance. The seal also has a smooth surface and good long-term oxidation resistance resulting in favorable long-term seal aging characteristics. This paper will also show the correlation of major coating properties and a comparison with another seal system used for the last 30 years. It will be demonstrated that the abradable seal is suitable for rubbing against untipped Ti based blades.