Combined cathodic arc/unbalanced magnetron grown CrN/NbN superlattice coatings for applications in the cutlery industry

Hard CrN/NbN superlattice coatings Δ=2.7 nm, were grown at low temperatures (250°C) by combined cathodic arc/unbalanced magnetron technique to coat knife blades produced from 1% carbon steel in an industrially sized four-target PVD coater. The deposition process combines the advantages of metal ion etching by Cr+ ions generated by steered arc discharge to guarantee high adhesion and unbalanced magnetron sputtering to deposit smooth CrN/NbN superlattice coatings The coatings’ structure, residual stress, the phase and the chemical composition have been investigated by XRD, SEM, X-TEM and SNMS techniques. The XRD measurements and hardness measurements revealed that the temperature treatment during the deposition process did not deteriorate the initial properties of the blade material. It was found that both the initial cutting power and the wear performance of the blades depend on the coating thickness and coating stoichiometry. CrN/NbN coatings with stoichiometric composition and thickness in the range of 3 μm showed the best compromise between initial sharpness and edge retention according to ISO cutting standards. Low-temperature CrN/NbN superlattice coated craft and textile blades showed an increase in lifetime by a factor of 10 when compared with uncoated ones and currently used Cr2O3 coated textile blades. The CrN/NbN proved to be superior to commercially available CrN and various carbon-based PVD coatings tested under the same conditions.