Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8023651 | Surface and Coatings Technology | 2018 | 7 Pages |
Abstract
Arc evaporated Al-Cr-N and Ti-Al-N are widely used protective coating materials due to their outstanding properties. While Al-Cr-N is known for its excellent oxidation resistance, Ti-Al-N exhibits interesting thermo-mechanical properties based on age hardening effects accompanying the spinodal decomposition upon annealing. Previous studies showed that the addition of Ta to Ti-Al-N further enhances the mechanical properties and oxidation resistance. In this work, we combine the beneficial properties of both systems (Ti-Al-Ta-N with a Ta content of about 7â¯at.% on the metal sublattice) in nano-scaled multilayer films with different bilayer periods of 15, 24, and 31â¯nm and total film thicknesses of 3 and 20â¯Î¼m, respectively. We found significantly higher hardness values of up to 35â¯Â±â¯2â¯GPa for the Al-Cr-N/Ti-Al-Ta-N multilayer coatings as compared with their monolithically prepared single phase face-centered cubic structured counterparts, Al-Cr-N with 28â¯Â±â¯2â¯GPa and Ti-Al-Ta-N with 32â¯Â±â¯2â¯GPa. All coatings exhibit a single phase face-centred cubic structure in the as-deposited state. Due to the formation of an Al-rich oxide scale, the high temperature oxidation resistance of the multilayer coating is nearly as good as that of Al0.62Cr0.38N, withstanding oxidation at 900â¯Â°C easily for >20â¯h with a parabolic growth rate constant of kpâ¯~â¯0.01â¯Î¼m2/h. Increasing the total film thickness to 20â¯Î¼m increases the measured hardness to up to 42â¯Â±â¯2â¯GPa and at the same time provides additional protection of the coated parts against oxidation.
Related Topics
Physical Sciences and Engineering
Materials Science
Nanotechnology
Authors
W.M. Seidl, M. Bartosik, S. Kolozsvári, H. Bolvardi, P.H. Mayrhofer,