Reaction Studies of Ceramic-Coated Tungsten

A coating consisting essentially of zircon and glass was fired in vacuum on tungsten wires. Coated wires were tested up to 10 hours at 3000°F. in an air atmosphere. Microstructural and X‐ray diffraction analyses indicated that the coating on the tested specimens consisted of glass and monoclinic zirconia and that certain tungsten oxides were present in the coating. These analyses also indicated that the probable mechanism of degradation in this type of coating may be attributed to the gradual migration of oxygen through the coating, with the resultant formation of tungsten oxides which then migrate to the coating surface and volatilize.