Abstract: A porous refractory object, more particularly a porous silicon carbide igniter is shown, the interconnecting pores and passageways of its body being filled with sub-micron sized silicon carbide particles deposited therein from a slurry coated on the surface of the object, which particles are subsequently oxidized at least on the surface and within the passages or pores in the subjacent surface portion of the body, to provide a protective coating of silica within the pores and on the surfaces of the object to preclude oxidation of the internal phases of the body of the object in oxidizing atmospheres.

Abstract: Porous refractory articles resistant to degradation at high temperatures for example by oxygen, chlorine and the like, are composed of a main body of a porous sintered carbide, nitride, boride or silicide which is coated with silicon nitride or silicon oxynitride. The coating is not only on the surface of the main body of the porous refractory article, but also penetrates the article to a depth at least greater than the depth of the surface pores.