Abstract: An article (22) is coated with a cermet coating (20) by first roughening and oxidizing the surface to be coated. A mixture is formed of a metallic powder having a mean particle size of less than about 5 micrometers, and a ceramic powder having at least some of the particle of a size less than the mean particle size of the metallic powder. The mixture of the metallic powder and the ceramic powder desirably has a coating coefficient of thermal expansion of about that of the article coefficient of thermal expansion after firing. The mixture of metallic and ceramic powders is slurried and applied to the prepared surface (24) of the article (22), preferably by spraying. The coated article is heated to an intermediate temperature to vaporize the carrier liquid, and thereafter to high temperature to sinter the coating.

Abstract: A method of forming high temperature resistant coatings from a quantity of composite particles, each comprising very small magnetic particles in a ceramic matrix by plasma spraying the composite particles onto a surface. Typically, the surface to be coated is pre-treated by a combination of solvent cleaning and abrasion, such as by grit blasting. In some cases the surface is coated with a thin electrically conductive transition layer having a coefficient of thermal expansion intermediate those of the surface and the composite coating. A quantity of finely divided composite particles are then prepared, each of the particles comprising a ceramic matrix containing plural spaced very small magnetic metal particles. In some cases, a small quantity of smaller pure matrix particles or lower melting particles are mixed with the composite particles to improve bonding.

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.