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

Abstract

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 r) of the films reached maximum values of H ~ 24 GPa and E r ~ 240 GPa for C Si ~ 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 C Si < 2.3 at.% in terms of the solid solution mechanism rather than the nanocomposite formation.