Adhesion Improvement Of Cvd Diamond Film By Introducing Cu/cr-diamond Composite Coated Interlayers

Low adhesion of CVD diamond film is a key factor restricting its practical application. Adhesion of CVD diamond was improved by introducing a metal-diamond composite coating prepared by composite plating. The morphology, the phase structure, the Raman spectra, the adhesion property and the growth process of these films were studied.There were three different methods to enhance the composite coatings:enhancing with (1) Cu plating depositing from citrate bath, with (2) Cr plating depositing from citrate bath trivalent chromium bath and with (3) Cu-Cr alloy plating depositing from fluoborate bath.The morphology of diamond films were studied by using scanning electron microscope (SEM). The result indicated that the continuity of diamond films was affect by the CVD deposition temperature. The lower deposition temperature, the faster the growth rate of diamond, the more inclined to form a continuous film. The granularity of embed diamond particles determined the roughness of CVD diamond film. The smaller size of embed diamond particles, the lower roughness of diamond film.The micro-XRD diffraction is used to identify the crystalline phase in the samples. (111), (220) and (311) peaks of diamond appeared in the XRD pattern. And the (111) peak was the strongest one. The Raman spectra showed that the quality of diamond films and crystallinity and the content of non-diamond carbon impurities were affected by the CVD temperature. It was easier to obtain diamond with high quality and crystallinity under higher CVD temperature.The adhesion of diamond films have been investigated under the indentation indented by using Vickers hardness tester. The result show that the diamond film enhancing with Cu-Cr alloy had the best adhesion property. In the CVD process, Cr of the coating reacted with C to form Cr3C2. As bonding phase, Cr3C2 could help to improve the adhesion between the film and the substrat. But it would reduse the adhesion if there is too much Cr in the coating for Cr3C2 is brittle phase.The growth processes of CVD diamond films were studied. During the primary process the main mode to grow diamond was homoepitaxy, and some new diamond crystal nucleus formed on the surface of heterogeneous coating. During the interim, some secondary crystal nucleus began to form on the big diamond particles, and diamond growth modes were both homogeneous and secondary nucleation.