Properties of TiN and CrN coatings deposited at low temperature using reactive arc-evaporation

Abstract

PVD TiN and CrN coatings were deposited at both low (≈200°C) and standard temperatures (≈400 °C) using reactive arc- evaporation. Variations in microstructure (obtained by TEM and XRD), morphology (studied using SEM) and chemical composition (determined by both EDS and GD-OES) were correlated to mechanical (residual stress state, microhardness) and tribological properties (scratch response, abrasive wear resistance). The results show a significant increase in hardness and residual compressive stress for the low-temperature TiN coating as compared with the standard-temperature coating. This was attributed to a drastic decrease in grain size and an increased compressive microstrain for the low-temperature coating. Moreover, the critical load and abrasive wear resistance of the low- temperature TiN coating had decreased as compared with the standard-temperature coating, although the hardness was significantly higher. This was due to the poor quality of the low-temperature TiN coating in combination with the high residual compressive stress. It is further shown that mechanical and tribological properties of the low-temperature CrN coating were comparable with the standard-temperature CrN coating, even though there was a difference in microstructure and chemistry.