Sundstrand Corporation

Robert W Fawley

James C Napier

Eric J Alexander

William Dean Treece

R G Keetley

An abradable coating is provided for use on a composite substrate which has a coefficient of thermal expansion substantially similar to that of the substrate and which is formed with a matrix resin of the same type of resin used to form the substrate. In particular, with a composite substrate formed from carbon or graphite fibers impregnated with a polyimide resin, an abradable coating formed from carbon or glass microballoons in a polyimide resin matrix has been found to avoid delamination as a result of thermal cycling between -65.degree. F. and 500.degree. F. Accordingly, that abradable coating is particularly suitable for use with composite compressor shrouds in gas turbine engines and aircraft auxiliary power units.

Abradable coating in a gas turbine engine

Combustors of gas turbine engines in which components are brazed to the combustor are not easily repairable by conventional welding because the brazed joint includes a melting point depressant which may not only cause the joint to be brittle but also the melting point of the joint to be near or below the temperatures required for welding. These problems are solved by a relatively simple and inexpensive process for producing a weld repairable combustor which includes using a brazing powder mix comprising a metal powder compatible with the metals of the combustor and the article to be brazed to the combustor, and suitable melting point depressant in powder form, heating the brazing powder mix to a first temperature sufficient to cause the brazing powder mix to become molten, and finally heating the brazing powder mix at a second temperature for a sufficient time to cause the melting point depressant to substantially diffuse away from the brazed area. The resulting combustor formed by this process can be repaired by welding when cracks or other discontinuities requiring a weld repair are situated near or at the brazed joint, and this process avoids the expensive requirement of redesign of the combustor to a welded combustor configuration which would require major tooling, equipment and processing changes.

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San Diego, CA, United States of America

Robert W Fawley