Development and characterization of CrN films by ion beam enhanced deposition for improved wear resistance

Chromium nitride (CrN) films were synthesized by ion beam enhanced deposition (IBED) process which involves using an argon ion beam to sputter the chromium target while using a nitrogen ion beam to bombard the deposited film. The surface and cross-section morphologies of CrN films were studied by scanning electron microscope (SEM) and atomic force microscope (AFM). The distribution of chemical composition was analyzed by X-ray photoelectron spectroscopy (XPS). The crystalline structures of thin films were identified by X-ray diffraction (XRD). The adhesion strength of film-substrate system was evaluated by the scratch test. Results showed that the ion bombardment energy and ion beam current density had significant effects on surface morphology, crystalline structure and adhesion strength of the deposited CrN films. With an increase in bombardment energy, the microhardness of the IBED CrN films increased, but the adhesion strength of the films decreased. Ion beam current density had a significant sputtering effect on the deposited CrN films. Wear tests were performed on a block-on-ring system under lubricated conditions and a ball-on-flat system under dry sliding condition. The data from both experiments showed that: (1) the wear resistance of GCr15 steel has been improved significantly after being coated with IBED CrN film: (2) thin films synthesized at lower bombardment energy or lower ion beam current density had better tribological properties.