Evaluation of CrAlN multilayered coatings deposited by PVD magnetron sputtering

The purpose of this experimental work is to evaluate the mechanical and tribological properties of chromium aluminum nitride (CrAlN) coating deposited on hypereutectic Al-Si-alloy. The microstructural, topographical analysis, and composition of CrAlN-coated substrates were examined by using scanning electron microscopy and energy-dispersive spectroscopy, whereas phase formation was analyzed by X-ray Diffractometer (XRD). Atomic force microscopy (AFM) images were taken from the substrate surface before and after the coating. The scratch adhesion of film-to-substrate was measured by using scratch machine. In an effort to understand the critical point, loads were identified by Scratch track in terms of load vs. depth as a function of scan distance. Moreover, the critical load as the beginning of chipping or spallation of the coating was studied. The tribological properties of CrAlN coating were evaluated by pin on disc tribometer at room temperature. XRD analysis showed that CrAlN successfully deposited with a preferential orientation along the (111), (200) and (220) peaks. The AFM images of coated sample confirmed that the surface roughness was lower(R-a=14nm) as compared to uncoated sample (R-a=46nm). The hardness of coated hypereutectic Al-Si-alloy was increased about 5.8 times as compared to uncoated sample. The coefficient of friction and wear rate of coated specimen were found to be improved. The coating adhesion strength of 2341mN was obtained with coating parameters for deposition of DC power (350W), RF power (200W), temperature (175 degrees C), and nitrogen flow rate (5%).