High-power impulse magnetron-sputtering thick metal/carbon–nitride-doped metal-matrix multilayer nano-composite coating can be applied to cutting-tool holder components to improve cutting insert’s life. One of the challenges of such an add-on solution is the poor adhesion between the thick coating and the hard alloy substrate, such as WC-Co shim. This work presents a study on WC-Co substrate surface preparation methods for HiPIMS coating and its adhesion improvement. Three mechanical surface pretreatment methods were investigated: machining (grinding), diamond polishing, and grit blasting. White-light interferometry was used for substrate surface texture measurement before and after pretreatment. It was demonstrated that, compared to machining and diamond polishing, grit blasting can significantly improve the interface adhesion between the ~200 µm-thick Cu:CuCN_x coating and WC-Co shim. Grit blasting was also found to be beneficial for improving the cutting insert’s life in the external turning process. In turning tests, the coating lifetime for grit-blasted shim was more than 90 min, whereas the coating lifetimes for machined shim (conventional shim) and diamond-polished shim were ~85 min and ~70 min, respectively. Further, by comparing the HiPIMS gradient chromium pre-layer between the coating and substrate for the different shims, the study also explained that the quasi-isotropic surface texture of grit-blasted shim is more advantageous for coating–substrate interface adhesion.

A thick 400-micron amorphous carbon nitride (a-CN_X) coating material was synthesized by means of plasma-enhanced chemical vapor deposition process. High-power impulse magnetron sputtering technique was used to sputter a pure graphite target plate in reactive argon (Ar), nitrogen (N₂) and acetylene (C₂H₂) environment for depositing the composite coating. Structural and chemical/elemental composition of the a-CN_X composite material was investigated by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and micro-Raman spectroscopy. The root-mean-square surface roughness (S_q) and structure were estimated by atomic force microscopy. Mechanical properties such as hardness and Young’s modulus (Oliver–Pharr method) at room temperature were characterized by Vickers micro-indentation test. Operational temperature test of the deposited a-CN_X coating reveals that it can withstand up to 400 °C without cracking. An inverted shaker test, based on central impedance method, was adopted to investigate the dynamic damping property of the coating material, and it was found that the first bending mode damping lossfactor of the reported a-CN_X coating is 0.015 ± 0.001 and corresponding loss modulus (Young’s modulus multiplied by lossfactor) is 0.234 ± 0.011 GPa.