A superhard CrAlSiN superlattice coating deposited by multi-arc ion plating: I. Microstructure and mechanical properties

A superhard CrAlSiN superlattice coating was deposited by multi-arc ion plating (M-AIP). The coating microstructure and mechanical properties were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), nano-indentation, scratch test and pin-on-disk tribo-test. The HRTEM results indicated that the CrAlSiN coating has a superlattice structure containing alternating fcc-(Cr, Al) N and h-(Al, Si) N layers with a period (λ) of 7.0 ± 0.2 nm. The coherent epitaxial growth structure was observed along {0001} plane of the h ‐(Al,Si) N phase and {111} plane of the fcc-(Cr,Al) N phase, due to the template effect of fcc-(Cr, Al) N crystal layer. The CrAlSiN coating exhibited a high hardness (52 GPa), high resistance to plastic deformation (H3/E⁎2 = 0.295 GPa), and high adhesion strength (critical load: 50 N). The wear test showed that the superhard CrAlSiN coating has a very low friction coefficient (0.1–0.2) against the counterpart material of WC/Co. The related mechanisms were discussed.