Mechanical properties and oxidation resistance of sputter deposited MoSi2 thin films

Abstract

Molybdenum disilicide belongs to the group of refractory transition metal silicides, being a highly attractive class of coating materials to withstand high-temperature oxidative environments. Due to the formation of a protective silicon-based oxide – obtaining a mixed metallic and covalent bonding character – MoSi2 exhibits an interesting combination of outstanding high-temperature oxidation resistance but also suitable mechanical properties. Within our study, we deposited MoSi2 thin films by direct current magnetron sputtering (DCMS) as well as high power pulsed magnetron sputtering (HPPMS) in pure Ar atmospheres. For the growth of the films an in-house developed (lab-scaled) deposition system was used. The influence of the deposition parameters (e.g. deposition pressure, temperature, or bias potential) on the phase formation and mechanical properties was investigated systematically. All coatings deposited were in-depth analyzed concerning their structure-mechanical properties, using a broad set of characterization techniques – i.e. scanning as well as transmission electron microscopy (SEM & TEM), X-ray diffraction (XRD), and nanoindentation. In addition, the oxidation kinetics were studied in detail using a combined differential scanning calorimetry/thermogravimetric system (DSC-TGA). The oxidation resistance was investigated in more detail for different temperature regimes up to 1500 °C.