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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";
Poster: 15th International Conference on Plasma Surface Engineering, Garmisch-Partenkirchen; 2016-09-12 - 2016-09-16.

Aluminium-chromium-based 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. 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-x
N 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.

AlxCr1-xN/(AlxCr1-x)2O3 multilayers