EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Modifying the architecture of multilayered hard coatings used in the metal cutting industry allows to tailor the mechanical properties such as hardness or fracture toughness of these coatings. Within this work, the effect of the bilayer thickness (Λ) and the individual layer thickness ratio on the microstructure and mechanical properties of ZrN/TiN multilayer coatings was investigated. Multilayer coatings with Λ on the μm scale (~300-600 nm) and two different ZrN:TiN thickness ratios of 6:1 and 3:1 as well as multilayers with Λ on the nm scale (<40 nm) were deposited by cathodic arc evaporation. In addition, TiN and ZrN single layers were synthesized. The microstructure was investigated by X-ray diffraction (XRD) and scanning electron microscopy. All coatings exhibit a face-centered cubic structure and a similar texture, which was predominantly (111). A columnar structure was observed for all samples and grain growth through the ZrN/TiN interfaces was discovered for all multilayer samples. For all coatings compressive residual stresses were determined by XRD using the sin²Ψ method, where the ZrN single-layer sample and the multilayer sample with the largest Λ exhibited the highest compressive residual stress of -1659 ± 163 GPa. Lower compressive residual stresses could be correlated with decreasing Λ and decreasing ZrN:TiN thickness ratio for the multilayer coatings. Micro-mechanical bending tests as well as nanoindentation experiments were conducted to assess the mechanical properties of the coatings. The obtained results allow to design a suitable architecture for ZrN/TiN multilayer coatings yielding the desired coating properties for application in the cutting industry.

Keywords: Fracture toughness, mechanical properties, multilayer, ZrN, TiN, arc evaporation