Understanding Local Bonding Structures of Ni-Doped Chromium Nitride Coatings through Synchrotron Radiation NEXAFS Spectroscopy

CrN has widespread applications as protective coatings, for example, in aircraft jet engines whereby their high hardness and good oxidation resistance render metal components resistant to harsh operating conditions. Alloying elements are commonly incorporated (doped) into the coatings to further enhance their thermomechanical properties. However, the effect of dopants on the electronic properties and their roles in modifying the grain boundary configurations remain unclear. Lack of such critical knowledge has hindered the development of design strategies for high performance CrN-based coatings. To address this challenging issue, in the present study near-edge X-ray absorption fine structure (NEXAFS) investigations of Cr1-yNiyN coatings at the Cr L-3,L-2-edge (570-610 eV), Ni L-3,L-2-edge (840-890 eV), and N K-edge (380-450 eV) regions were conducted using synchrotron radiation soft X-ray (SXR) spectroscopy in both Auger electron yield (AEY) and total fluorescence yield (TFY) modes. The chemical states in CrNiN were found to change with the increase of Ni content, manifested as a small chemical shift and moderate change of shapes of various absorption edges. The CrN grain size also became smaller with increasing Ni concentration. These findings help improve our understanding of local bonding structures, which could potentially lead to improved coating designs for highly demanding applications.