FORMATION OF COATINGS BY PLASMA SPRAYING MAGNETIC-CERMET DIELECTRIC COMPOSITE PARTICLES

摘要

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. The composite particles are plasma sprayed onto the surface to be coated at temperatures such that only the surfaces of the composite particles are melted, thereby permitting higher magnetic material loadings without forming an excessively electrically conductive coating. The resulting coating is durable, has high temperature resistance and absorbs incident microwave energy.