Ti3SiC2-SiC multilayer thin films deposited by high temperature reactive chemical vapor deposition

Abstract

Ti3SiC2-SiC multilayer film coatings synthesis was investigated with the high temperature reactive chemical vapor deposition technique. The method consists of a reaction between SiC (as the substrate and interlayers) and H2-TiClx gaseous mixture. Cross-section morphologies and phases were studies by scanning electron microscopy (SEM), X-ray diffraction (XRD) and automated crystal orientation mapping in transmission electron microscopy (ACOM-TEM). Thermodynamic calculations were carried out to select more appropriate gas composition for reactor conditions and understand the chemistries of reaction between layers in the different steps. Nano and Vickers micro-indentation mechanical tests determined hardness and elastic modulus of the Ti3SiC2 and Ti5Si3Cx surfaces samples. Oxidation tests and emissivity measurements allowed the evaluation of Ti3SiC2-SiC coatings as materials for high temperature applications. The multilayered systems kept their mechanical integrity and showed low degradation after 25 h of thermal cycles at 900 °C in air. The measurement of the optical properties also revealed an increase of the absorptivity after the oxidation of Ti3SiC2 surface sample.