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

High cutting performance and long tool life time are the ongoing demands in the machining industry in order to increase the productivity. Hard and wear resistant coatings with superior hardness and at the same time increased toughness are required to achieve these goals. Within this work, strategies to simultaneously improve the hardness and fracture toughness of TiN based coatings grown by chemical vapor deposition are investigated. The addition of B to TiN or Ti(C,N) is accompanied by grain refinement, which results in a significant improvement of the hardness and fracture toughness. Within the Ti(C,N) system, the most beneficial mechanical properties were obtained for a moderate to high C/(C+N) ratio. In addition to the chemical composition, the coating architecture has been identified as an important influence factor for the mechanical properties. As the individual layer thickness in TiN/Ti(B,N) multilayer coatings decreases, an improvement of the hardness and fracture toughness was observed. Within the investigated coatings, the highest hardness was obtained for monolayered Ti(B,C,N) (32.2±1.4 GPa), whereas a TiN/Ti(B,N) multilayer coating with a bilayer period of 100 nm exhibited the highest fracture toughness (5.8±0.5 MPam^1/2). Based on the results of this study, CVD hard coatings with improved damage tolerance can be produced, which enables to maximize the real-life cutting performance.