A comparative research on physical and mechanical properties of (Ti, Al)N and (Cr, Al)N PVD coatings with high Al content

Arc ion plating (Ti0.34, Al0.66)N and (Cr0.28, Al0.72)N coatings are deposited onto cemented carbide substrates at 350 °C. The crystal structure and microstructure of the deposited coatings are characterized by means of X-ray diffraction (XRD), electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD examination indicates that both (Ti0.34, Al0.66)N and (Cr0.28, Al0.72)N coatings are of fcc structure. The atomic ratios of Al against Ti (Cr) for the two coatings are approximately close to those of the alloy targets according to EPMA measurement. In accordance with SEM observation, the fractured cross-section of the (Cr0.28, Al0.72)N coating is composed of columnar crystallites repeatedly interrupted by a renucleation process. Based on SEM and TEM methods, the cross-sectional fracture of (Ti0.34, Al0.66)N coating is found to show nano-crystalline feature without appearance of the columnar structure. (Cr0.28, Al0.72)N coating exhibits better wear resistance, approximately equal adhesion with the substrate, but lower nano-hardness compared with (Ti0.55, Al0.45)N coating.