Titanium carbide coating with enhanced tribological properties obtained by EDC using partially sintered titanium electrodes and graphite powder mixed dielectric

• Combination of electrode and dielectric is used to prepare TiC coating by EDC.
• Mechanisms of reduced friction and wear rate for the coatings are explored.
• It shows COF of about 0.1 and 18 times lower wear rate than the counterpart.

The combination of partially sintered titanium tool electrode and graphite powder mixed dielectric is proposed to prepare titanium carbide coatings by electrical discharge coating technique with the major objective to improve their tribological properties. The phase composition and microstructure of the obtained coatings are characterized by X-ray diffraction, Raman spectrum, transmission electron microscopy and scanning electron microscopy. Their tribological performances are investigated by ball-on-disk tribometer and the corresponding mechanism of friction and wear is explored. Compared with the coatings obtained in dielectric without graphite powder, they show more uniform thickness and higher microhardness. They also show lower and steadier friction coefficient as well as better wear resistance especially in high load condition. These enhanced properties can be attributed to the suspended graphite powders in dielectric. They, as the additional carbon source, increase the transition of titanium tool electrode to titanium carbide and introduce amorphous carbon into the coatings. It is this amorphous carbon that continuously supplies the lubricant at the contact, helping to accommodate sliding motion and preventing the surfaces from mechanical wear and oxidation.