Influence of C content on the structure, mechanical and tribological properties of CrAlCN films in air and water-based cutting fluid

CrAlCN films with different C concentrations ranging from 0 to 75.3 at% were deposited on AISI M2 high-speed steels using magnetron sputtering. Besides their structure and mechanical properties, the tribological performances of CrAlCN films in air and water-based cutting fluid were also compared. The results showed that CrAlN film consisted of most fcc-CrN/Cr2N and less fcc-AlN. After C incorporation, the amount of fcc-CrN/Cr2N in CrAlCN films still kept stable relatively in addition to the more formation of amorphous carbon (a-C). As a consequence, the hardness of CrAlCN films increased firstly to the highest value of 1095.2 +/- 56.8 HV0.01 at the C content of 50.3 at%, but then declined slightly. However, the critical loads of CrAlCN films decreased gradually from 14.8 +/- 2.7 to 7.9 +/- 0.9 N as the C content increased from 0 to75.3 at%. High C content in CrAlCN films resulted in the more formation of a-C, thus contributing to a decrease in friction coefficient of CrAlCN/SUS440C tribopairs both in the air (from 1.06 to 0.47) and water-based cutting fluid (from 0.60 to 0.11). In the meantime, the CrAlCN film containing the highest C content (75.3 at%) showed the minimum wear rate because of the lowest friction coefficient in both friction environments. As compared with the tribological performances of CrAlCN films in air, the CrAlCN films were more suitable to be used in water-based cutting fluid condition.