Diamond coating adhesion on WC − 6 %Co tools: A systematic study

Achieving a consistent and well-adhering diamond coating remains a challenge for WC-Co tools. We analyze the microstructure of tungsten carbide and cobalt using electron microscopy and diffraction techniques. We examine batches with good and poor layer adhesion at three stages: uncoated, after pretreatment, and after coating. The samples are differentiated based on their magnetic saturation value. This study focuses on WC-6 %Co with a mean WC grain size of 1.2 μm and vanadium doping. The results reveal a direct correlation between magnetic saturation and diamond coating adhesion to the substrate surface. Magnetic values represent the tungsten content and, consequently, the corrosion resistance of the binder phase (cobalt). An ignoble binder (low corrosion resistance) is prone to excessive etching and improper diamond nucleation. Batches with a noble binder show consistent coating formation, consistent diameter reduction, and consistent depletion zone depth. In contrast, batches with an ignoble binder exhibit significant changes in these areas. • The presence of relatively high percentage of hcp Co can be an indication for high magnetic saturation value of WC-Co. • Magnetic saturation of WC-Co is directly related to the amount of tungsten dissolved in the binder phase (Co) • Magnetic saturation is an indicator of binder quality and therefore affects the etching procedure for diamond coating. • Relatively high magnetically saturated samples show unstable matrix and deep etching of cobalt, whereas low magnetically saturated samples show consistent and stable etching.