Microstructure, mechanical properties and cutting performance of Cr 1-y Ta y N single layer and Ti 1-x Al x N/Cr 1-y Ta y N multilayer coatings

Abstract 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 ~ 22.2 and ~ 25.2 GPa, respectively. For the arc evaporated coatings, a hardness of ~ 22.7 could be determined for the multilayer, while for the single-layers the hardness increased from ~ 21.6 to ~ 24.3 GPa with increasing bias voltage. Ball-on-disk tests against alumina at room temperature, 500 and 700 °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.