From a large number of growth defect density measurements on samples from industrial production batches, we performed statistical analysis in order to evaluate the influence of deposition parameters on the defect surface density. We analyzed various PVD hard coatings (TiN, TiAlN, CrN, TiAlN/a-CN, nanostructured AlTiN/TiN and TiAlSiN/TiSiN/TiAlN layers) prepared by different PVD deposition techniques (thermionic arc evaporation, magnetron sputtering) at various deposition conditions. We found that the defect density on various samples in the same batch scatters a lot. There can also be a substantial difference on the two faces of the same sample. This suggests that the formation of growth defects is sporadic and spatially localized. The defect density depends on sample position, deposition time, type of coating material, and batching material. The influence of steel inclusions on coating growth was also analyzed. In order to understand the effects of different inclusions and other irregularities the substrate surface morphology was followed from the cleaning to ion etching and deposition. Shallow craters and voids were observed at positions of MnS inclusions, while the growth of TiAlN/CrN nanolayer coating on SiO2 inclusions was coherent.
COBISS.SI-ID: 27288615
Our program group member Dr Matjaž Panjan spent his postdoc at the prestigeous Lawrence Berkeley National Laboratory (USA), supported by the Fullbright fellowship. Together with the Berkley coworkers they proposed a model for ion transport in high-power pulsed magnetron sputtering, which was published in Applied Physics Letters. The model is based on the discovery of inhomogeneous plasma structures, called the ionization zones; in the magnetron plasma they rotate in the direction E×B. In this model they proposed that within the ionization zones the electron and ion densities are spacially separated and thus cause the formation of an electric field in azimutal direction. This electric field rotates together with the zones. The ions are mainly formed within the ionization zones therefore they acquire the kinetic energy of the rotating electric field, which accelerates them up to the energy of 100 eV or more.
COBISS.SI-ID: 27099687
Deep cryogenic treatment used in combination with classic vacuum heat treatment shows a significant improvement in wear resistance of high speed steel tools and their applications. In coated tools, the properties of substrate material have a great influence on the properties of the coating. The aim of this research was to investigate how the microstructure of the substrate which was altered by deep cryogenic treatment influences the properties of TiAlN coating and the properties of the substrate/coating adhesive joint. The substrate material in this research was high speed steel produced by powder metallurgy, grade PM S390 MC. The specimens were heat treated in two ways, conventionally in vacuum and using deep cryogenic treatment. After heat treatment, a part of specimens was ion nitrided. Four groups of specimens were PVD coated with TiAlN coating. It was found that the improvement in substrate properties by the precipitation of very fine eta-carbides during the deep cryogenic treatment will influence the substrate/coating adhesive joint.
COBISS.SI-ID: 26920743