US 5,211,991 AGranted

Method of plasma spraying magnetic-cermet dielectric coatings

AssigneeHughes Aircraft Company

InventorRonald E. Bullock

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Abstract

A method of forming high temperature resistant coatings having magnetic particles in a ceramic matrix by plasma spraying. Typically, the surface to be coated is cleaned by a combination of solvent cleaning and abrasion, such as by grit blasting. A mixture of ceramic particles and metal particles is provided and the mixture is plasma sprayed onto the surface using a sufficiently large proportion of metal particles to form a conductive first coating layer. A second layer is plasma sprayed with a mixture having a gradually decreasing metal particle content. A third layer is plasma sprayed using a mixture having a sufficiently low proportion of metal particles as to be dielectric. A pattern of small, spaced, conductive areas is then formed on the surface of the third layer. The resulting coating is durable, high temperature resistant and absorbs incident microwave energy.

Claims4

Dependent claims

The method of forming a magnetic-cermet dielectric coating on a substrate surface which comprises the steps of:

providing a quantity of finely divided electrically insulating ceramic particles having average diameters of from about 10 to 45 micrometers and a quantity of finely divided magnetic metal particles having average diameters of from about 10 to 45 micrometers;
mixing together portions of said ceramic and said metal particles to produce a first mixture having about 50 vol % of each type of particles;
plasma spraying said first mixture onto a substrate to form a first layer having a thickness of from about 3 to 5 mils;
continuing to plasma spray said first mixture onto said first layer while gradually reducing the metal content to about 10 vol %, to form a transitional layer having a total thickness of from about 6 to 10 mils;
mixing additional quantities of said metal and ceramic particles to a substantially uniform second mixture having about 5 to 10 vol % of metal particles, the balance being ceramic particles;
plasma spraying said second mixture onto said transitional layer to form a top layer having a thickness of from about 30 to 50 mils.

3 more elements

Dependencies are inferred from the claim text.