CVD-Diamond

CVD-diamond coatings were tested, which were deposited on commercial WC-Co cutting tools by a high current DC-arc (HCDCA) process that is based on the decomposition of methane under the assisting action of hydrogen. Film thickness was found to be d = 7.1 and 7.2 µm, respectively. The surface quality of the cemented carbide substrate was varied by different etching to study the effect of the surface morphology on the quality of the diamond-coated tools.
The measurement results are shown in Figure 1.

Example 5
Figure 1: Laser-acoustic measurements for WC-Co cutting tools coated with CVD-diamond, substrate pretreatment was varied

The slopes of the measured dispersion curves are distinctly different. This indicates that the Young’s moduli of these diamond coatings are different. The modulus of 1160 GPa (Pretreatment 1) is close to the tabulated value of diamond and showss a high quality and perfect diamond structure of this coating. The value of 486 GPa obtained for Pretreatment 3 is far from being satisfactory for a diamond coating. The modulus reduction was caused by enhanced porosity and defect density in the region near the interface. This accompanies with a distinct reduction of the mechanical wear resistance tested by sandblasting (Figure 2), although Raman spectroscopy indicated the same diamond bonding structure for all coatings [1].

Example 6

Figure 2: Correlation of Young’s modulus E with the sandblast time tB for detaching the coating

[1] G. Jörgensen, M. Lahres, B. Schultrich, P. Burck, H.-J. Scheibe, D. Schneider, J. Karner, Proceedings of the 14th International Plansee Seminar, Eds. G. Kneringer, R. Rödhammer and P. Wilhartitz, Plansee AG, Reutte (1997), Vol.

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