Quaternary diborides—improving the oxidation resistance of TiB<sub>2 ± z</sub> coatings by disilicide alloying
A. Bahr, O. Beck, T. Glechner, Alexander Grimmer, Tomasz Wójcik, Philip Kutrowatz, J. Ramm, O. Hunold, S. Kolozsvári, P. Polcik, Eleni Ntemou, Daniel Primetzhofer, H. Riedl
Abstract
To overcome the limited oxidation resistance of the emerging class of transition metal borides, we suggest within this study novel quaternary diborides, Ti-TM-Si-B2 ± z (TM = Ta, Mo), achieving the compromise between excellent oxidation resistance and requirements of hard coatings. Single-phase AlB2-type structured Ti-TM-Si-B2 ± z films (3–5 µm) are sputter-deposited from TiB2/TMSi2 targets. The Ti-Ta-Si-B2 ± z coatings exhibit 36 GPa in hardness, while maintaining strongly retarded oxidation kinetics till 1000°C. Ti-Mo-Si-B2 ± z coatings preserve a hardness up to 27 GPa, although outperforming all their counterparts by featuring outstanding oxidation resistance with 440 nm oxide scale thickness after 1 h at 1200°C.