Development of CVD WC–Co coatings

To address the problem of high speed machining titanium and its alloys, a CVD process to deposit WC–Co coatings on high-temperature deformation resistant substrates was developed. The WF6–CH4–H2 and CoCl2–H2 systems were used to deposit the WC and Co phases, respectively. Characterization by scanning electron microscopy revealed a microstructure similar to that of commercially available sintered WC–Co. X-Ray diffraction confirmed the presence of two distinct phases in the co-deposited coating. Although adhesion was not a problem on cemented carbide substrates, a functionally graded interfacial coating was used to improve adhesion to ceramic substrates. Turning tests were performed on Ti–6% Al–4% V alloy to evaluate the machining characteristics of these coatings. These tests demonstrated that the coatings considerably enhanced chemical wear resistance and therefore can be effectively used for high speed machining of Ti alloys.