| AVS 63rd International Symposium & Exhibition | |
| Advanced Surface Engineering | Tuesday Sessions |
| Session SE+NS+TF+TR-TuM |
| Session: | Nanostructured Thin Films and Coatings |
| Presenter: | Helmut Riedl, TU Wien, Institute of Materials Science and Technology, Austria |
| Authors: | H. Riedl, TU Wien, Institute of Materials Science and Technology, Austria B. Kohlhauser, TU Wien, Institute of Materials Science and Technology, Austria V. Paneta, Uppsala University, Sweden C.M. Koller, TU Wien, Institute of Materials Science and Technology, Austria S. Kolozsvári, Plansee Composite Materials GmbH, Germany D. Primetzhofer, Uppsala University, Sweden P.H. Mayrhofer, TU Wien, Institute of Materials Science and Technology, Austria |
| Correspondent: | Click to Email |
The outstanding oxidation resistance, thermo-mechanical stability and chemical inertness of Al2O3 attracts particular attention in various industrial applications. Especially, in the field of protective barrier coatings there are many research activities focusing on the synthesis of the different polymorphs α- and γ-Al2O3 (corundum and cubic), respectively. Apart from the fact that the deposition of the thermodynamically stable α-Al2O3 is strongly limited by the depositing temperature, the formation of electrically isolating Al2O3 at the target surface leads to massive arcing processes and destabilizes the deposition process. These problems could be overcome by varying the powering method to pulsed DC and especially RF sputtering, but at the cost of decreased deposition rates and plasma densities.
Therefore, we study in detail the influence of small amounts of transition metals such as M = Cr, Nb, Mo, and W on the process stability and coating properties of reactive DC sputter deposited (Al1-xMx)2O3 thin films. To keep the influence of the alloying elements on the outstanding properties of alumina as low as possible only targets with alloying contents of x = 2 and 5 at.% are investigated. All micro-alloyed targets allow for significantly improved process stability and massively reduced arcing processes at the target as compared to the non-alloyed Al target. The morphology of all coatings deposited is highly dense, smooth and partly columnar with cubic γ-Al2O3 crystalline structure. The mechanical properties of the Cr, Mo, and W containing coatings are slightly enhanced by solid solution hardening in comparison to pure Al2O3 obtaining e.g. hardness values of about 25 GPa. In contrast, alloying contents of about 1 at.% Nb are already degrading the mechanical properties of alumina thin films. The significantly enhanced process stability when using Cr, Mo, and W alloyed Al targets, leads to coatings with improved thin film quality. Therefore, the oxidation resistance of these films even outperform the Al2O3 DC sputtered film.