NONDESTRUCTIVE CHARACTERIZATION OF CVD DIAMOND FILMS ON CEMENTED CARBIDE CUTTING TOOLS

Cemented carbide tools coated with diamond have been proved to show su perior performance for machining non-ferrous alloys, especially alumin um alloys. The development of efficient CVD technologies for the depos ition of polycrystalline diamond up to an industrial scale allows thei r broader industrial application. However, the strong influence of the deposition conditions and of the substrate morphology on the film pro perties requires adequate characterization methods to optimize the dia mond coatings and to control the deposition process. To overcome the l ack of suitable characterization methods, investigations were performe d 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 Al Si10Mg). Whilst Raman spectroscopy characterizes the quality of the di amond structure, Young's modulus allows the presence of defects and th e quality of the interface to be evaluated. Depending on the depositio n technology and the pretreatment of the substrates, an enhanced poros ity and weaker interface strength were detected. A correlation of Youn g's modulus with the results of the sandblast test was found. (C) 1998 Elsevier Science S.A.