Microstructure, mechanical properties and cutting performance of Cr1-yTayN single layer and Ti1-xAlxN/Cr1-yTayN multilayer coatings

Cr1-yTayN single-layer and Ti1-xAlxN/Cr1-yTayN multilayer hard coatings were deposited on cemented carbide substrates using magnetron sputter deposition and cathodic arc evaporation. For the sputtered coatings a bias voltage of -50 V was applied, while arc evaporated coatings were deposited at three different bias voltages of -40, -60 and -80 V. The coatings were grown from powder metallurgically produced CrTa targets with a composition of 75 at% Cr and 25 at% Ta, resulting in a Cr/Ta ratio of 71/29 in the sputtered coatings and 74/26 in the arc evaporated coatings, independent of the applied bias voltage. All coatings are characterized by a single-phase face centered cubic structure. The sputtered single- and multilayer coatings exhibited a hardness of similar to 22.2 and similar to 25.2 GPa, respectively. For the arc evaporated coatings, a hardness of similar to 22.7 could be determined for the multilayer, while for the singl e-layers the hardness increased from similar to 21.6 to similar to 24.3 GPa with increasing bias voltage. Ball-on-disk tests against alumina at room temperature, 500 and 700 degrees C yielded wear rates comparable to conventional Ti1-xAlxN coatings, but significantly lower friction coefficients. The performed cutting tests also showed promising results, indicating the high application potential of Cr1-xTaxN-based hard coatings.