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 (C-Si) in the films. Microstructure, composition and mechanical properties were studied as a function of C-Si using XRD, ERD-TOF and depth-sensing indentation. Three regions of C-Si were distinguished: (i) C-Si < 2.3 at.%, where the grain size (D) does not significantly change with increasing C-Si; (ii) 2.3<C-Si<6.7 at.%, where D decreases as C-Si increases; and (iii) 6.7 <= C-Si <= 11.6 at.%, where a relatively rapid decrease of D is observed with increasing C-Si. We found that the hardness (H) and the reduced Young's modulus (E,) of the films reached maximum values of H similar to 24 GPa and Er similar to 240 GPa for C-Si similar to 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. (c) 2008 Elsevier B.V. All rights reserved.