Structure and hardness studies of CN_x/TiN nanocomposite coatings

Crystalline CN_x/TiN multilayer composite coatings have been synthesized using an opposed cathode unbalanced magnetron sputtering system. Electron microscopy studies showed that the CN_x/TiN coatings were fully crystalline and dense at small bilayer thicknesses. An amorphous phase was formed when the CN_x layer thickness exceeded 4-5 nm. Two new d spacings extracted by Fourier transform of digitized images of the crystalline CN_x region cannot be matched by known compounds formed by the detected elements. This provides limited evidence for the possible formation of a new carbon-nitrogen compound. Nanoindentation hardness about 45-55 GPa was reproducibly achieved for coatings produced under low nitrogen partial pressure and high substrate bias (-150 to -250 V). TiN (111) preferred orientation was strongly correlated to the high coating hardness.