Abstract
Hard coatings deposited by physical vapor deposition are state of the art for wear and oxidation protection of cutting tools. The cutting performance depends on coating material and process as well as cutting edge microgeometries. Both have an influence on the thermomechanical tool loads resulting in tool wear. Therefore, a process adapted design for the consideration of the entire system is necessary. One approach to substitute costly machining investigations and save material resources is the use of finite element (FE)-based chip formation simulations. However, in order to perform these simulations, information about chemical, thermal and physical coating behavior in the temperature range relevant for machining is necessary. In the present study, nanocomposite TiAlSiN coatings with varying coating thicknesses were deposited on cemented carbide tools. The effect of coating thickness on coating morphology, chemical composition, thermal conductivity as well as indentation hardness at ϑ = 20 °C, ϑ = 200 °C, ϑ = 400 °C and ϑ = 600 °C was analyzed. Therefore, three coating variants with a coating thickness of ds = 2 μm, ds = 4 μm and ds = 6 μm were deposited. Additionally, the distribution of the heat, generated during turning 42CrMo4 + A, was simulated for the coated cutting tool. A columnar morphology with constant chemical composition was determined for the variants. While the arithmetic mean value of the coating roughness increased with increasing coating thickness, there was no influence of coating thickness on thermal diffusivity and high temperature coating hardness measurable. Nevertheless, an influence of the tool temperature can be observed in the application behavior in turning tests as well as in the simulation, possibly caused by a change in the contact conditions due to increasing cutting edge microgeometry by increasing coating thickness. Regarding the tested TiAlSiN hard coatings no significant influence of the coating thickness on properties such as thermal diffusivity and indentation hardness were observed. This leads to the assumption, that even when the coating thickness is changed no significant changes in the FEM simulation are needed, which makes modelling easier.
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