Regular Article

On the study of the mechanical properties of Mo-B-C coatings^*

¹ Department of Physical Electronics, Faculty of Science, Masaryk University, Kotlářská 2, 61137 Brno, Czech Republic
² Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, 61662 Brno, Czech Republic

^a e-mail: zerafel@mail.muni.cz

Received: 1 December 2015
Revised: 14 April 2016
Accepted: 21 April 2016
Published online: 8 August 2016

Abstract

Mo₂BC thin films show a favourable combination of high stiffness, hardness and elastic modulus together with moderate ductility. In this study we focused on the comparison of mechanical properties of Mo-B-C thin films with different structures (nanocrystalline or amorphous). The thin films were deposited on steel, hard metal and silicon substrates using DC magnetron sputtering. The mechanical properties of Mo-B-C films were studied using indentation techniques under both quasistatic and dynamic conditions using a wide range of loads from 50 μN up to 1 N. The results showed that even amorphous Mo-B-C thin films had high hardness of 19.5 ± 0.5 GPa and elastic modulus of 276 ± 5 GPa. Their hardness is comparable with the common amorphous diamond-like carbon coatings. Moreover, their fracture toughness is significantly higher. The results of mechanical tests were correlated with microstructure observations carried out using scanning and transmission electron microscopy. The images of the deformed area under the residual indentation imprints showed no cracking even after high loads or after indentation with sharp cube corner indenter.