Effects of pulsed direct current power supply on ta-C coatings: Microstructure, mechanical properties and tribocorrosion behavior

The wear and corrosion of cemented carbides pose substantial challenges to maintaining the reliability and extending the service life of marine engineering equipment under severe maritime conditions. In this study, a self-enhanced magnetron sputtering system combined with a straight-tube filtered cathode vacuum arc deposition system was employed to fabricate tetrahedral amorphous carbon (ta-C) coatings on cemented carbides. Four distinct coatings were prepared using a 70 A direct current power supply and a pulsed direct current power supply with peak currents varying from 300 to 500 A. The results indicate that the application of pulsed current power significantly improves the surface quality of the coatings and increases their sp3 content. As the peak pulse current increases, the energy of C ion bombardment gradually rises, leading to a trend in which the mechanical and physical properties of ta-C coatings initially improve before declining. The coating prepared with a peak current of 400 A exhibits the best wear rate (3.6 x 10-6 mm3 center dot N- 1 center dot m- 1) and the best electrochemical stability (open current potential = -0.3 V), which can be attributed to its superior coating composition (sp3 fraction = 72 %), improved resistance to plastic deformation (H3/E*2 = 0.8 GPa) and fewer coating defects.