Evaluation of a flexible physical vapor deposited TiC–C coating system

Abstract

Physical vapor deposited (PVD) TiC–C coatings with different amounts of free carbon have been investigated with respect to their microstructure, mechanical and tribological properties. The coatings were deposited using a plasma assisted PVD process which combines evaporation of titanium and sputtering of carbon. The carbon content was controlled by means of the magnetron power. X-ray photoelectron spectroscopy was used to study the chemical composition. X-ray diffraction and transmission electron microscopy were utilised to obtain information about phase composition and microstructure. It was found that the mechanical properties varied immensely with the carbon content in the coatings. Coating hardness and elastic modulus both decreased dramatically with increasing carbon content. The hardness dropped from 44 to 13 GPa, and the elastic modulus from 430 to 160 GPa, as the carbon content was increased from 43 to 70 at.%. All coatings provided very low friction coefficients, between 0.14 and 0.20, as tested against a steel ball in a ball-on-disc test. The TiC–C coating system proved to be easy to control with respect to mechanical properties. Together with good tribological properties this makes it possible to tailor these coatings to suite different applications as well as substrate materials.