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R. Hollerweger, L. Zhou, D. Holec, R. Rachbauer, P. Polcik, P.H. Mayrhofer:
"Structure and Mechanical Properties of Ta alloyed Cr-Al-N coatings";
Poster: International Conference on Metallurgical Coatings and Thin Films, ICMCTF 2014, San Diego, CA, USA; 2014-04-27 - 2014-05-02; in: "Abstract Book ICMCTF 2014", (2014).

Transition metal alloying of Cr1-xAlxN based coatings is commonly used to improve their mechanical properties and thermal stability. Recent reports show that Tantalum additions to Ti1-xAlxN type coatings positively influence their properties, but only little information is available on the effect of Ta on Cr1-xAlxN based coatings. Consequently, we have performed a combined experimental and ab initio based study on the influence of Ta additions (0, 2, 6, 12, and 26 at% on the metal sublattice) on structure and mechanical properties of arc evaporated Cr1-x-yAlxTayN coatings with Al/(Cr+Al) ratios > 0.61. With increasing Ta-content the droplet number density decreases and coating surface smoothens, which is much more pronounced as with increasing the bias voltage from -40 to -120 V. Simultaneously, the columnar structure observed for Ta-free Cr0.37Al0.63N significantly changes into a fine grained structure (crystallite size ~5 nm) with clearly reduced columnar character. Additionally,
increasing the Ta content favors the formation of a preferred 200 growth orientation resulting in a reduction of the indentation moduli from ~500 to ~375 GPa, which is in agreement with ab initio calculations. As the hardness of our coatings remains at ~35 GPa with increasing Ta content, this indicates an increase in fracture toughness at still high resistance against plastic deformation.