Influence of Mo on structure-mechanical properties of TiB2±z coatings

Abstract

Transition Metal Diboride (TMB2) thin films deposited by physical vapor deposition (PVD) are gaining a lot of attention in industry and academia as next generation protective coatings for diverse applications. So far, TMB2 are known for their refractory character involving high hardness, thermal stability as well as chemical inertness. However, one weak point of these ceramic coating materials is their limited fracture resistance. Here, different theoretical studies [1,2] suggest novel alloying strategies – forming ternary TMBs – to reduce their brittle behavior.

Therefore, in this study we investigated the influence of Mo on the structure-mechanical properties of Ti-Mo-B2±z coatings. Different coatings were grown by DC magnetron sputtering using 6-inch powder metallurgically manufactured TiB2, TiB2/MoB 95/5 mol%, TiB2/MoB 90/10 mol%, as well as TiB2/MoB 80/20 mol% targets. To gain a detailed insight on the structure-morphological properties, a broad set of characterization techniques was used – i.e. electron based microscopy (SEM & TEM), X-ray diffraction (XRD), Nanoindentation, or Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The fracture toughness was evaluated by micromechanical cantilever bending tests. Furthermore, the oxidation behavior was investigated using a thermogravimetric system. In summary, Mo influences the growth behavior of α-structured TiB2±z films, leading to nanocrystalline but more stoichiometric coating materials. The fracture behavior and super-hardness of Ti-B2±z thin films are not dominated by Mo.

[1] V. Moraes, et al., Sci. Rep. 8 (2018) 9288. [2] B. Alling, et al., Sci. Rep. 5 (2015) 9888.