Influences of target power and pulse width on the growth of diamond-like/graphite-like carbon coatings deposited by high power impulse magnetron sputtering

Abstract

In this paper, diamond-like carbon (DLC)/graphite-like carbon (GLC) composite coatings were deposited by using high-power impulse magnetron sputtering (HIPIMS). The effect of HIPIMS mean power and pulse width on the surface morphology, carbon atomic bonding structure, mechanical properties, compressive stress, and tribological performance of the DLC/GLC coatings were characterized using laser scanning confocal microscopy, Raman spectroscopy, nano-indentation, compressive stress tester, and ball-on-plate tribometer, respectively. The results show that the mean power and pulse width have significant influence on the formation of GLC microparticles and sp3 C-C content. Both increasing mean power and/or decreasing pulse width could increase the target current density, causing the enhancement of the ionization rate of carbon and subsequently improving the sp3 fraction of the coatings. Increasing pulse width would extend the arc discharge time, resulting to an increase in the amount and size of the GLC microparticles. The mechanical properties and compressive stress dominantly depend on the sp3 C-C fraction of the coatings. But the coating tribological performance shows a significant relationship with the embedded GLC microparticles that can help to decrease the friction coefficient. However, the relatively soft GLC microparticles would decrease the coating wear resistance. It is believed that the tribological performance of the DLC/GLC coatings can be controlled via adjusting the HIPIMS parameters.