Microstructure and mechanical properties of Cr–Si–N coatings prepared by pulsed reactive dual magnetron sputtering

Cr–Si–N thin films were deposited by pulsed DC reactive dual-magnetron sputtering using Cr and Si targets, while various currents applied to the Si target allowed one to vary the Si content (CSi) in the films. Microstructure, composition and mechanical properties were studied as a function of CSi using XRD, ERD-TOF and depth-sensing indentation. Three regions of CSi were distinguished: (i) CSi < 2.3 at.%, where the grain size (D) does not significantly change with increasing CSi; (ii) 2.3 < CSi < 6.7 at.%, where D decreases as CSi increases; and (iii) 6.7 ≤ CSi ≤ 11.6 at.%, where a relatively rapid decrease of D is observed with increasing CSi. We found that the hardness (H) and the reduced Young's modulus (Er) of the films reached maximum values of H ~ 24 GPa and Er ~ 240 GPa for CSi ~ 2.3 at.%. Based on the evolution of the microstructural and mechanical properties of the Cr–Si–N films, we propose to explain the hardening observed for CSi < 2.3 at.% in terms of the solid solution mechanism rather than the nanocomposite formation.