Toughening effect of Ni on nc-CrAlN/a-SiN _x hard nanocomposite

To combat the brittleness of hard nc-CrAlN/a-SiN _x nanocomposite (nc-: nanocrystalline, a-: X-ray amorphous), different Ni content (from 0 to 39.8 at.%) is doped via magnetron sputtering. Glancing Angle X-ray Diffractometry, X-ray photoelectron spectroscopy, Field Emission Scanning Electron Microscopy and Transmission Electron Microscopy are employed to investigate the microstructural evolution. With increased Ni, the grain size decreases accompanied with morphology change, from dense glassy to coarse columns. With 4.2 at.% Ni, scratch toughness of nc-CrAlN/a-SiN _x hard nanocomposite (28 GPa) is improved by around 200% at expense of only 18% hardness.