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

Owing to their advantageous properties such as a high hardness and good oxidation resistance, Ti(Al)SiN protective hard coatings can be used for metal cutting applications. Within this work, the microstructure of arc evaporated TiN, TiSiN and TiAlSiN coatings with low Al contents of 3 and 14 at.% was correlated with their mechanical properties. X-ray diffraction (XRD) as well as scanning electron micrographs of the cross-sections revealed a pronounced grain refinement upon addition of Si and Al to TiN. Furthermore, XRD pole-figures showed a change in texture of the coatings from a (111) preferred orientation for TiN to a (200) texture for Ti(Al)SiN coatings. A significant increase in hardness of more than 10 GPa when adding Si and Al to TiN was detected by nanoindentation. In order to gain a more detailed insight into the mechanical properties of the Ti(Al,Si)N coatings, micromechanical bending tests were conducted that showed an enhanced fracture stress and fracture toughness ($K_{IC}$) for Ti(Al)SiN compared to TiN. Hereby, the initially rather low $K_{IC}$ value of 2.4 ± 0.3 MPa√m for TiN could be increased to 3.3 ± 0.2 MPa√m for the TiAlSiN coating with an Al content of 14 at.%. The present findings provide a systematic overview of the microstructure and mechanical properties of arc evaporated Ti(Al,Si)N coatings, thus allowing to assess the suitability of these coatings for the cutting industry.

Keywords: hard coatings, arc evaporation, Ti(Al)SiN, micromechanical testing