| Summary: | Diamond-like carbon (DLC) films have been extensively studied for more than two decades due to their highly attractive properties. These films exhibit unique mechanical, chemical and electronic properties and thus, possess great potential for applications in tribology. However, two drawbacks in the DLC films are high level of internal stress developed during growth preventing deposition of thick films and low thermal stability. Synthesis of Me-DLC (Cr-DLC and N-doped Cr-DLC) presents a way to overcome these drawbacks. In the present study, DLC, Cr-DLC and N-doped Cr-DLC films were deposited on Si substrate using a hybrid Plasma assisted CVD/PVD process. Film characterization in terms of microstructure, structure, composition and chemical state of components was carried out by transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS) of the Cr-DLC as well as N-doped Cr-DLC films. Mechanical properties of the films were characterized by microhardness testing. The tribological properties were studied by conducting pin-on-disc experiments. Optical profilometry was used to analyze intrinsic stress in the films and the wear profiles and wear rate.
TEM and XPS showed that N-doping results in formation of CrN along with Cr carbide in the film. N-doped Cr-DLC films were found to possess higher hardness than the Cr-DLC and DLC films. N-doped Cr-DLC exhibited lower intrinsic stresses while maintaining a comparable friction coefficient and wear rate as well as higher microhardness. The low intrinsic stresses of N-doped Cr-DLC show promise for the deposition of thicker coatings, while maintaining desirable mechanical and tribological properties.
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