Non-destructive characterization of CVD diamond films on cemented carbide cutting tools

Cemented carbide tools coated with diamond have been proved to show superior performance for machining non-ferrous alloys, especially aluminum alloys. The development of efficient CVD technologies for the deposition of polycrystalline diamond up to an industrial scale allows their broader industrial application. However, the strong influence of the deposition conditions and of the substrate morphology on the film properties requires adequate characterization methods to optimize the diamond coatings and to control the deposition process. To overcome the lack of suitable characterization methods, investigations were performed to combine structural properties (Raman spectra), Young's modulus of the coatings, and mechanical erosion tests (sandblast test), and the machining behavior of diamond-coated cemented carbides (drilling of AlSi10Mg). While Raman spectroscopy characterizes the quality of the diamond structure, Young's modulus allows the presence of defects and the quality of the inte rface to be evaluated. Depending on the deposition technology and the pretreatment of the substrates, an enhanced porosity and weaker interface strength were detected. A correlation of Young's modulus with the results of the sandblast test was found.