Abradable material composition, a thermomechanical part or casing including a coating, and a method of fabricating or repairing a coating presenting said composition

Abstract

The invention relates to an abradable material composition comprising a resin-based matrix, in particular a silicone matrix together with filler comprising hollow beads. In characteristic manner, the hollow beads withstand high temperatures and are made of refractory material. The hollow beads are preferably made of an alumino-silicate material. The composition is applicable to making abradable coverings for compressor casings, in particular casings for compressors of the low pressure type or of the booster type, or for a fan, the covering being in register with moving blades.

Description

[0001] The invention relates to an abradable material composition (or a material that can be machined by moving parts), to a thermomechanical part (such as a casing) comprising a metal substrate covered in a wear portion comprising a covering presenting such a composition, and to a turbomachine fitted with such a thermomechanical part. [0002] The invention also relates to a method of fabricating or repairing an abradable covering on a metal substrate and presenting such a composition. BACKGROUND OF THE INVENTION [0003] In turbine engine applications, for portions that are said to be “cold”, i.e. for which the operating temperature does not exceed 250° C., there are to be found wear portions made of an abradable material composition comprising resin. [0004] That type of abradable material is generally constituted by a matrix of hot-polymerizable resin, in particular a silicone resin, and a filler of hollow glass beads, for example. [0005] Hollow glass beads are microspheres serving f...

AI Technical Summary

Benefits of technology

[0010] An object of the present invention is to provide an abradable material composition for which the wear debris is capable of withstanding high temperatures, and a method of obtaining a part covered in said material whose wear debris can withstand temperatures that are higher than those that can be withstood by presently-proposed compositions.

[0011] A particular object of the present invention is to overcome the drawbacks of prior art abradable materials in order to avoid permanently clogging ventilation perforations or cooling channels of small size due to hollow glass beads melting.

[0012] To this end, according to the present invention, the hollow beads are made of refractory material, glass being excluded, so that said beads present greater resistance to high temperatures.

[0013] It can thus be understood that by using refractory hollow beads that present a melting temperature that is much higher than that of glass beads, the problem of the hollow beads melting is avoided and they remain solid at the temperatures to which they are subjected, even in the hottest part of the turbomachine.

[0014] This solution also presents the additional advantage of making it possible to use hollow beads that are less expensive than glass beads, particularly if the hollow beads are combustion residues from fossil fuel power stations or steelworks, in particular if they are constituted by blast furnace slag.

[0015] Overall, by means of the solution of the present invention, it is possible to improve the high temperature behavior of the wear debris from abradable materials, and in particular it is possible to avoid the abrasion residues formed from the hollow beads melting in the hottest portions of turbojets.

Problems solved by technology

The use of silicone resins has replaced the earlier use of organic resins which present insufficient mechanical strength, and, on being abraded, give rise to powder that, on combustion, creates residues that deflagrate at high temperatures and under high pressures.

Those small perforations or small-diameter channels thus tends to become clogged easily and to be difficult to clear with ventilation pressure differences, thereby leading to local interruption of ventilation for the moving blades of the turbine, and thus to potentially major operating problems due to high temperatures, and possibly endangering the ability of the blades to maintain mechanical strength, or indeed leading to local melting.

At operating temperatures and in the event of a large amount of particles being given off during contact between the moving part and the abradable portion, it has been found that the use of hollow glass beads in abradable portions situated in particular upstream from the high pressure turbine, e.g. in the low pressure compressor, can lead to said material melting as it passes through the high pressure compressor, with the material then clogging the openings of the ventilation perforations in permanent manner.

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