Cemented carbide tools used for cutting operations are nowadays coated with thin hard coatings deposited by means of physical (PVD) or chemical vapor deposition (CVD). Within this thesis, focus was set first on the coating deposition technology, where emphasis was laid on the most relevant single contributions to the different deposition techniques, with an additional special focus on the pretreatment of substrates before coating deposition. The second focus was set on the application behavior of cutting inserts coated by CVD with TiCN/Al2O3, where the deposition process inherent thermal crack network within the coatings and the wear occurring during turning of steels was investigated. The introduction of Sankey diagrams enabled to visualize the contributions to the deposition processes in matters of material and energy consumption, offering the opportunity to identify potential savings. By modifying etching time and ion energy during pretreatment of cemented carbide substrates by ion etching in PVD processes, changes of surface topography could be illuminated, pointing out that sharp edges of cutting inserts with delicate geometries represent crucial regions for this process step. The effect of coating post-treatment by wet blasting on the tensile thermal crack network in CVD TiCN/Al2O3 hard coatings on cemented carbide substrates was visualized by a detailed scanning electron microscopy investigation, showing that besides smoothing of the coating surface also the present cracks are closed. A subsequent temperature rise, e.g. during vacuum annealing or turning of steel, results in re-opening of these tensile cracks, which creates pathways for diffusion processes through the coating’s bulk. An investigation of the dominating wear mechanisms occurring during turning of various steels led to the conclusion that wear is governed by the used cutting speed and the workpiece material.
|Translated title of the contribution
|Hartstoffschichten auf Wendeschneidplatten: Prozesstechnologie und Anwendung
|Published - 2018
Bibliographical noteembargoed until null
- hard coatings
- cemented carbide cutting tools
- ion etching