| AVS 63rd International Symposium & Exhibition | |
| Advanced Surface Engineering | Wednesday Sessions |
| Session SE+TR-WeM |
| Session: | Protective Coatings for Tribological Applications in Surface Engineering |
| Presenter: | Christian Martin Koller, Technische Universität Wien, Austria |
| Authors: | C.M. Koller, Technische Universität Wien, Austria A. Kirnbauer, Technische Universität Wien, Austria H. Bolvardi, Oerlikon Balzers, Liechtenstein P. Polcik, Plansee Composite Materials GmbH, Germany P.H. Mayrhofer, Technische Universität Wien, Austria |
| Correspondent: | Click to Email |
In recent years, different approaches towards the enhancement of physical vapor deposited TiAlN hard coatings were made. Among these, the alloying of additional elements to form quaternary compounds proved to be extremely efficient. In addition to as-deposited film properties also the coatings’ thermo-mechanical behaviour and the performance in oxidizing environments, both constitute fundamental requirements for cutting applications, can be significantly increased.
One example is the substitution of Ti or Al by Ta, which chemically strengthens the face-centred cubic cell, leading to higher hardness values and increased Young’s moduli. Furthermore, Ta prevents the formation of anatase TiO2by directly promoting rutile-structured TiO2. Consequently, a thermal-induced phase transformation of anatase into rutile TiO2 and its therewith associated generation of crack networks is avoided.
In the present study two subsets of multilayers based on TiAlN/TaAlN and TiAlTaN/TaAlN were investigated. The coatings were synthesised using powder-metallurgically manufactured Ti0.5Al0.5, Ta0.9Al0.1, Ta0.75Al0.25, Ta0.5Al0.5, Ti0.475Al0.475Ta0.05, and Ti0.45Al0.45Ta0.10 targets. The TiAlN and TiAlTaN-base layers were arc evaporated (arc), whereas the TaAlN layers were either arc evaporated or reactively sputtered (rsd) [1][2]. The multilayer architecture was realised by the use of a shutter system or through the continuous two-fold rotation of the substrate holder, resulting in sharp and slightly burred layer interfaces. The overall Ta-content and TaAlN–layer thickness was varied by different power settings of the Ta0.75Al0.25 cathode and shutter-open times, respectively.
We can show that a coating architecture of TiAlNarc and TaAlNarc allows for thermo-mechanical properties comparable to TiAlTaN, whereas superior oxidation resistance only can be achieved by a TiAlNarc/TaAlNrsd arrangement. For both rsd-multilayer arrangements the critical factor in terms of thermo-mechanical performance and oxidation resistance is the TaAlN layer thickness as well as the overall interface volume. Results are discussed based on X-ray diffraction and electron microscopy studies.
[1] C.M. Koller, R. Hollerweger, C. Sabitzer, R. Rachbauer, S. Kolozsvári, J. Paulitsch, P.H. Mayrhofer, Surf. Coat. Technol.259 (2014) 599–607.
[2] C.M. Koller, R. Hollerweger, R. Rachbauer, S. Kolozsvári, J. Paulitsch, P.H. Mayrhofer, Surf. Coat. Technol.283 (2015) 89–95.