Influence of composition on the wear properties of boron carbonitride (BCN) coatings deposited by high power impulse magnetron sputtering

We investigate boron-carbon-nitride (BCN) coatings deposited with high power impulse magnetron sputtering (HiPIMS) technology and conventional pulsed DC sputtering for their application as wear resistant coatings. Especially for BCN coatings, HiPIMS qualifies as a promising deposition technology as the short pulses with very high power density result in a high ionization degree of the plasma species, allowing a manipulation of the film structure and properties. Both, carbon and boron nitride can hybridize in sp2 or sp3 configuration or a mixture of both, so that coating features such as hardness and coefficient of friction can be tailored to meet the requirements of special applications. We studied the influence of different carbon sources and deposition modes on the composition and tribological properties of BCN films, including microhardness, friction coefficient, and thermal stability. Additionally, we investigated thermal degradation mechanisms by interpreting X-ray photoelectron spectra (XPS). We observed that the application of either pulsed DC or HiPIMS pulse mode has a significant influence on the microhardness and thermal stability of the coatings, in which HiPIMS mode generally provides higher hardness and better thermal stability. Furthermore, we found that samples co-sputtered from B4C and graphite target show superior hardness and thermal stability compared to those sputtered reactively with acetylene.