STRUCTURAL BEHAVIOR OF SPUTTERED W-C-CO COATINGS AT INCREASING TEMPERATURES

In order to evaluate the thermal resistance of sputtered W-C-Co coatin gs, a structural study was carried out on amorphous and crystalline co atings according to their cobalt content after having been annealed at increasing temperatures up to 800-degrees-C. All the films were stabl e up to 700-degrees-C, at which temperature the amorphous films began to crystallize as alpha-W2C; for higher temperatures the alpha-W2C car bide evolves to M6C, the extent of which increases the higher the coba lt content; for low cobalt content films WC carbide was also formed. C rystalline films have similar structural transformations, although the M6C phase is almost non-existent and alpha-W2C and WC can occur with preferential orientations. In all cases, the films after annealing wer e carbon-deficient in relation to the results obtained for the as-depo sited conditions; in spite of the fact that the phases detected after crystallization are also carbon-deficient, these results are not consi stent which implies that some free carbon should exist in the annealed films.