Effect of the carbon content on the structure and mechanical properties of Ti-Si-C coatings by cathodic arc evaporation

Ti-Si-C coatings with various carbon contents were synthesized on cemented carbide substrates by a TiSi (88:12 at.%) alloy cathode in acetylene (C2H2) plasma atmosphere with a flow rate of 15 to 40 sccm using a dual source cathodic arc evaporation system. Experimental results showed that the structure and the mechanical and wear properties of Ti-Si-C coatings were strongly dependent on the carbon content (or acetylene flow rate). When the carbon content is lower than 46 at.%, the Ti-Si-C coating was comprised of an fcc NaCl-type TiC phase, a small volume fraction of Ti3SiC2 metallic phase, and an amorphous SiC phase. When the carbon content was increased above 50 at.%, the Ti3SiC2 metallic phase was reduced and nanocrystalline TIC (nc-TIC) and amorphous SiC (a-SiC) and carbon phases (a-C) were observed. The coatings could be characterized as TiC nanocrystallites imbedded in an amorphous SiC, C and free carbon matrix, resulting in the hardness evidently enhanced to 40 GPa as the carbon content was increased at about 52 at.%. When the carbon content was further increased to above 54 at.%, the volume fraction of amorphous carbon significantly increased, the fraction of the crystalline phases decreased, and both the hardness and the wear resistance decreased. (C) 2010 Elsevier B.V. All rights reserved.