METHOD FOR SELECTIVELY COATING A PORTION OF A SUBSTRATE WITH A GAS-CARRIED SUBSTANCE

摘要

A method for applying a diffusion coating of a substance to a portion of substrate comprising applying a deposition coating to a particular surface of an object by applying an active gas containing the coating substance in a form which will react with the surface to form a coating. Instead of masking portions of the object not to be coated, or applying an absorbent paste, a second neutralizing or "killer" gas is introduced in the regions where the coating gas may be present, but where no coating is desired. The neutralizing gas is of a type which will reduce the reactivity of the coating substance in the active gas. As a result, formation of a coating in undesired areas is substantially prevented.