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18th Plansee Seminar - 2013
Robert Hollerweger (R. Hollerweger)
Poster
"Phase Stability, Thermal Stability and Oxidation Resistance of Arc-Evaporated Ti-Al-Ta-N Coatings"
Hollerweger R.1, Arndt M.2, Rachbauer R.2, Polcik P.3, Paulitsch J.4, Mayrhofer P.H.4
1Christian Doppler Laboratory for Application Oriented Coating Development at the Institute of Materials Science and Technology, Vienna University of Technology, Austria
2OC Oerlikon Balzers AG, Liechtenstein
3PLANSEE Composite Materials GmbH, Germany
4Institute of Materials Science and Technology, Vienna University of Technology, Austria
Alloying Ti-Al-N with Ta has proven to enhance the hardness, thermal stability and oxidation resistance of sputter deposited coatings. To meet a balance between all these requirements for protecting tools during drilling and cutting applications, an optimized chemical composition of Ti, Ta and Al within the cubic stability range is necessary. However, only limited information is available on arc-evaporated Ti-Al-Ta-N coatings. Therefore, coating developments with an industrial scaled INNOVA Oerlikon Balzers plant, using powder metallurgical (Ti0.50Al0.50)0.95Ta0.05, (Ti0.50Al0.50)0.90Ta0.10, (Ti0.34Al0.66)0.95Ta0.05 and (Ti0.34Al0.66)0.90Ta0.10 targets, were carried out and investigated with respect on their phase stability, mechanical properties as well as thermal stability and oxidation resistance. Vacuum annealing treatments exhibit retarded film decomposition by the addition of Ta. Consequently, the formation of the stable wurzite AlN phase is shifted to higher annealing temperatures of ~1200C, accompanied by the formation of hexagonal Ta2N. Furthermore, alloying Ta to Ti-Al-N promotes the formation of a dense oxide scale. Therefore, the Ti-Al-Ta-N coating is still intact under a protective oxide, even when treated at 950C for 20h in ambient air.
 


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