Growth of α-(Al,Cr)2O3 Thin Films by Reactive r.f. Magnetron Sputtering
D. Diechle, M. Stüber, H. Leiste (Harald.Leiste@imf.fzk.de),
S. Ulrich, Forschungszentrum Karlsruhe, Germany, V. Schier, Walter AG,
The 36th International Conference on Metallurgical
Coatings and Thin Films,
Posterpräsentation, Hard Coatings and Vapor Deposition Technology, Symposium B Poster Session30.04.2009
Advanced thin film materials for cutting tool applications require complex roperty profiles including high hardness, toughness, wear and corrosion resistance. Such materials are expected for example in the Al-Cr-O system. The materials science approach behind this work is to quench Al-Cr-O thin film materials in a metastable corundum-type solid solution structure directly from the vapor phase at deposition temperatures significantly below the temperature range of the thermodynamic stable phase which exists only above 1300°C in the corresponding Al-Cr-O phase diagram. First, we will describe a combinatorial approach using a segmented target consisting of aluminum and chromium plates for the deposition of Al-Cr-O thin films by reactive r.f. magnetron sputtering. This experimental procedure results in the growth of coatings of different composition and microstructure in dependence of the sample positions in relation to the target. For specific deposition conditions stoichiometric, nanocrystalline solid solution strengthened (Al1-x,Crx)2O3 thin films were grown in a corundum-type structure. Secondly, we derive from these experiments fixed individual material compositions and use homogeneous metallic targets with an appropriate Al:Cr composition for reactive r.f. magnetron sputtering. Similar coatings grown by these different approaches will be compared with respect to their constitution, microstructure and properties. The deposition experiments are carried out with a Leybold Z 550 PVD machine in an argon–oxygen plasma. The cathode power is set to 500 W in r.f. mode, and the total gas pressure is 0.65 Pa in all experiments. During deposition the substrate temperature is controlled in the range from 180°C to 600°C. In addition, a substrate bias up to -400 V is induced with a second r.f. power supply. Commercial cemented carbide substrates and silicon wafers are coated. The coatings are characterized by determining their thickness, Vickers micro hardness, residual stress, density, chemical composition, constitution (by XRD) and their microstructure (by REM and TEM).