This work analyzes a novel amorphous carbon coating, deposited via Plasma-Assisted Chemical Vapor Deposition, on two cemented carbide substrates containing fine (6CoF) and medium-sized (6CoM) tungsten carbide grains, both with 6 wt% cobalt binder. These materials are essential for drilling and milling tools in the manufacturing industry due to their exceptional balance of hardness and fracture toughness. Conventional structural and phase analyses were performed using scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. Beyond these techniques, the coating-substrate interface was investigated at the nanoscale using advanced scanning transmission electron microscopy approaches, including innovative four-dimensional STEM and electron energy loss spectroscopy, enabling direct insight into the local sp 2 carbon bonding configuration and the crystallographic orientations present within the hard-metal substrate. The average of the WC grain size was 0.52 ± 0.27 and 1.2 ± 0.53 μm for 6CoF and 6CoM, respectively. A consistent 40 nm thick amorphous transition layer was identified at the coating-substrate interface in both samples. Phase analysis revealed that the substrate was primarily composed of hexagonal tungsten carbide, while the binder phase consisted of both cubic and hexagonal cobalt. The amorphous carbon coatings contain sp 2 ratio ranging from 36.1 ± 14.6 % for 6CoF and 28.6 ± 6.6 % for 6CoM; however, the latter also contains some polycrystalline regions. Overall, this combined methodological approach provides unprecedented nanoscale insight into carbon bonding and substrate crystallography, offering a deep understanding of interface formation in amorphous carbon coated cemented carbides.
Beatriz et al. (Fri,) studied this question.