ADHESION STRENGTH OF DIAMOND FILM ON CEMENTED CARBIDE INSERT

We have been studying diamond coatings on cemented carbide for cutting tool applications. To improve the adhesion strength of diamond film, a cemented carbide insert which contains a metal belonging to group 4a or 5a was heat treated before coating. A thin solid solution layer, w hich contains a large amount of this metal but no cobalt, was formed o n the surface of the heat-treated carbide insert. The diamond film dep osited onto the heat-treated insert showed a high adhesion strength, b ecause the surface of the solid solution layer was very rough. The cut ting performance of the diamond-coated insert was almost the same as t hat of a sintered diamond insert.