Effect of H2 dilution on the structure and properties of nc-CrC/a-C:H coatings deposited by a hybrid beams system

Abstract

Nanocomposite CrC/hydrogenated amorphous carbon (nc-CrC/a-C:H) coatings were deposited by a hybrid beams system comprised of a hollow cathode ion source and a cathodic arc ion-plating unit with varying H2 flow rates. The influences of H2 flow rates on the morphologies, microstructures, and properties of the coatings were systematically studied. The morphologies and microstructures of the coatings were characterized by SEM, AFM, XPS, Raman spectroscopy, GIXRD, and HRTEM. The mechanical and tribological properties were measured by a nano-indenter, scratch tester, and ball-on-disk tribometer. The wear tracks were evaluated using 3D profilometer, optical microscope, and EDS analysis. It has been found that a moderate H2 flow rate can effectively smooth the surface, enlarge the fraction of a sp3 bond, and improve the properties. The coating exhibits the highest hardness and elastic modulus at the H2 flow rate of 40 sccm. A superior combination of adhesion strength, friction coefficient, and wear resistance can be achieved at the H2 flow rate of 80 sccm.