A COMPARISON STUDY OF DIAMOND FILMS GROWN ON TUNGSTEN CARBIDE COBALT TOOL INSERTS WITH CH4 AND CF4 GAS SOURCES

The results of a comparison study of continuous diamond coatings deposited on tungsten carbide-6% cobalt tool inserts using CF4 and CH4 gas sources are presented. The CH4 grown diamond film utilizes a thin (1200 angstrom) amorphous silicon interlayer for adhesion while the CF4 diamond film is deposited directly onto the tool insert. The films are characterized by scanning and transmission electron microscopy, and Raman spectroscopy and are diamond. Diamond films produced with CF4 gas have much higher (nearly a factor of 4) growth rates and better adhesion (about a factor of 3) than diamond films grown with CH4 gas. An aluminum-17% Si alloy is machined with the diamond-coated tool inserts to determine their performance in a machining environment. Using CF4, diamond is believed to grow by first removing the tungsten from the tungsten carbide to expose the underlying carbon atoms. Subsequent carbon containing gaseous species can then bond to the exposed carbon and initiate and propagate diamond growth.