Mechanical and Structural Properties of Nanocomposite CrAlSiN-AlSiN Coating with Periodically Modulated Composition

A nanocomposite CrAlSiN-AlSiN coating with periodically modulated composition was developed and investigated regarding the effect of the composition and structure on the mechanical properties. The modulation was performed by variation of the pressure, cathode current and bias voltage during deposition. The structure and composition of the coating were investigated by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) analyses. The coating had a nanocomposite structure consisting of (CrAl)N and (AlSi)N nanograins embedded in a Si3N4 matrix. The EDS analysis of the cross-section revealed that the period composition had changed from Cr051Al0.41Si0.08N to Al0.82Cr0.04Si0.14N. It was shown that the elastic modulus could be adjusted by composition modulation. The coating hardness of 54 GPa was obtained by nanoindentation. The modulated CrAlSiN-AlSiN coating exhibited improved elastic strain to failure (H/E* = 0.11, H-nanohardness, E*-the effective elastic modulus), excellent resistance to plastic deformation (H-3/E*(2) = 0.72), and elastic recovery of 70%, which suggested improved toughness.