Microstructure, stress and mechanical properties of arc-evaporated Cr-C-N coatings

The relationships between coating microstructure and properties in the Cr-C-N system have been investigated as a function of composition and post-deposition annealing. Coatings of varying compositions were grown using are-evaporation, by varying the reactive gas how ratio f(R) =f(C2H4)/f(N-2) from 0 to 0.2, and were found to consist primarily of the cubic delta -Cr(C,N) phase. Changes in both the unstressed lattice parameter, a,,, and X-ray diffraction background intensity indicate that both the carbon concentration within the delta -phase and amorphous/crystalline content increases with f(R). Increasing f(R) also decreases the magnitude of the compressive biaxial residual stress, from approximately 6 to 1 GPa, while increasing both the inhomogeneous stress and thermal stability. The elastic modulus and hardness of as-deposited coatings were determined from nanoindentation to be 320 and 23 GPa, respectively, for moderate carbon concentrations (f(R) less than or equal to 0.05). Concurrent variations in microstructure and hardness with post-deposition annealing indicate that the as-deposited hardness is significantly enhanced by the microstructure, primarily by lattice defects and related stresses (microstresses) rather than average stresses (macrostresses). (C) 2001 Elsevier Science B.V. All rights reserved.