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R. Raab, S. Kolozsvári, R. Rachbauer, P.H. Mayrhofer:
"Influence of multilayer arrangement on structure and mechanical properties of arc evaporated oxide, nitride, and oxide/nitride coatings within the systems Al-Cr-N and Al-Cr-O";
Talk: 43rd International Conference on Metallurgical Coatings and Thin Films (ICMCTF), San Diego (USA); 2016-04-25 - 2016-04-29; in: "43rd ICMCTF International Conference on Metallurgical Coatings and Thin Films", (2016), 49.

Cathodic arc evaporation, being an extremely successful and widely used physical vapour deposition (PVD)
technology, features high flexibility for the preparation of protective coating systems. Aluminium-chromiumbased
oxides and nitrides, for instance, are typically applied to cutting and forming tools, or milling devices,
owing to their outstanding thermo-mechanical properties, wear and oxidation resistance, representing crucial
capabilities for such forming and machining tools.
Another major benefit of cathodic arc evaporation is the possibility to significantly influence the coating
microstructure by the adaption of deposition parameters, which allows for enhanced and specifically tailored
properties.
In this regard, we have studied the architectural design and resulting mechanical properties of Al-Cr-based oxide,
nitride, and oxide/nitride coatings. Therefore, AlxCr1-xN and (AlxCr1-x)2O3 multilayers as well as mixtures thereof
were synthesised by reactive arc evaporation using powder metallurgically prepared Al0.7Cr0.3 targets. By careful
adjustment of deposition time and reactive gas configuration, the individual (AlxCr1-x)2O3, AlxCr1-xN, and
multilayers could be designed with different bilayer periods and interfaces. Scanning electron microscopy (SEM)
analyses revealed the influence of the deposition time per layer to the architectural structure and surface topology.
By reducing the time per layer during the deposition (thus increasing the total number of layers), the (AlxCr1-x)2O3
and AlxCr1-xN layers have different thicknesses, resulting in a decreased bilayer period, decreasing roughness and
an increasing hardness. According to TEM and XRD results the Al-Cr-based multi-layered coatings indicate a
single phase face centred cubic (fcc) structure with a preferred (200) and (220) orientation. With decreasing layer
thickness, we observe a slight shift of the diffraction peaks to higher 2ϴ angles, which suggests reduced
compressive stress formation. Evaluation of the full width at half maximum, based on the B1-like cubic (200)
XRD peak, reveals a lower grain size for coatings with lower deposition time per layer.
Based on our results we can conclude that arc evaporation and the knowledge-based reactive gas flow control and
arrangement leads to AlxCr1-xN/(AlxCr1-x)2O3 multilayers with excellent hardnesses and moderate surface
rouhgnesses, when the bilayer period is optimized.

Al-Cr-based, oxide, nitride, multilayer, architecture, interface, cubic structure