Avco Corporation

William H Doddman

Subhash K Naik

Alfred De Ferrari

Abradable wall structures for high temperature applications, such as in turbine housings and the like. The wall structures comprise a superalloy metal base plate supporting a superalloy metallic cellular structure, the cells of which are filled to a substantial extent with at least one ceramic core material providing high heat resistance, oxygen barrier and low thermal expansion properties. The invention involves the application of a porous or pore-forming surface composition to provide a corrosion-resistant, erosion-resistant abradable outer surface layer, the softness or porosity of which can be tailored to improve the abradability of the wall structure, while imparting oxidation-, corrosion- and erosion-resistance to the structure. The surface layer composition may comprise metal superalloy, ceramic or cermet base compositions containing fugitive or retained inert filler materials.

Process for making abradable hybrid ceramic wall structures

Abradable hybrid ceramic wall structures

A powder feed system with a recirculator is provided for a plasma spray apparatus so that spraying operations may be started and stopped abruptly. The subject system utilizes a pressurized gas to direct a powdered material from a powder feed hopper to the plasma spray applicator. A diverter valve is located intermediate the powder feed hopper and the plasma spray applicator and in close proximity to the plasma spray applicator for selectively diverting the powdered material toward or away from the plasma spray applicator. Powdered material diverted away from the plasma spray applicator is directed to a powder accumulator for subsequent reuse. The powdered material is kept in continuous motion during both spraying and diverting operations thereby avoiding the need to overcome inertia each time spraying operations are commenced. Furthermore, because of the close proximity of the diverter valve to the plasma spray applicator, spraying operations may be started and stopped abruptly with little or no transition period of variable flow rate. In a preferred embodiment the powder accumulator is in communication with the powder feed hopper thereby facilitating the recirculation and reuse of the diverted powdered material.

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Guilford, CT, United States of America

William H Doddman