Mechanical properties, bonding characteristics, and oxidation behaviors of Nb–Si–N coatings

Abstract Nb–Si–N coatings with Si contents of 0–30 at% were fabricated through reactive direct current magnetron cosputtering. The processing parameters were various sputtering powers, substrate holder rotation speeds, and nitrogen flow ratio (N 2 /(N 2  + Ar)). Three phase regions, namely face-centered cubic (f.c.c.) NaCl structure, X-ray amorphous, and nanocrystalline phases, were identified and related to the chemical compositions of the coatings. Low-Si-content (0–13 at%) and middle-N-content (39–45 at%) Nb–Si–N coatings exhibited an f.c.c. structure, high-Si-content (17–30 at%) and high-N-content (45–53 at%) Nb–Si–N coatings exhibited an X-ray amorphous structure, and low-Si-content (6 at%) and low-N-content (26–30 at%) Nb–Si–N coatings exhibited a nanocrystalline structure. Examining the bonding characteristics of the Nb–Si–N coatings by using X-ray photoelectron spectroscopy indicated that NbN tended to form preferentially and was followed by Si 3 N 4 , which is consistent with the laws of thermodynamics. The correlations between the mechanical properties, residual stresses, and structures of the Nb–Si–N coatings were investigated using nanoindentation, a curvature method, and X-ray diffraction. The oxidation behaviors of the Nb–Si–N coatings annealed in air at 400–600 °C were also examined.