RESIDUAL STRESS IN ARC-EVAPORATED Cr-C-N COATINGS

摘要

The interrelationship between coating microstructure and properties in Cr-C-N system is nvestigated as function of composition and annealing temperature. Coatings of varying compositions were grown using arc-evaporation, by varying the reactive gas flow ratio f_R=f(C_2H_4)(N_2), and found to consist primarily of the cubic δ-Cr(C,N) phase. Macro- and microstresses were measured using x-ray diffraction sin~2ψ and peak broadening techniques, respectively, and both were found to change considerably with fg ratio. In addition, the unstressed lattice parameter a_o was determined by employing sin~2ψ curves taken at different annealing temperatures, and the resulting values indicate increasing carbon concentration with f_R ratio. 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=0.05). Concurrent variations in microstructure and hardness with annealing temperature indicate that as-deposited hardness is significantly enhanced by microstructure, primarily by lattice defects and related microstresses rather than macrostresses.