Porous nanocrystalline Ti(C_xN_{1 - X}) thick films by plasma electrolytic carbonitriding

Nanocrystalline Ti(C_xN_{1 - x}) films on titanium were prepared by plasma electrolytic carbonitriding (PEC/N) at 600 V in an electrolytic solution containing triethanolamine and formamide using a pulse power supply. XRD, EDAX, FESEM and TEM were employed to characterize the phase components, element composition, and microstructure of the films. Rockwell C indenter and Vicker's indentation test were used to evaluate the adhesion and hardness of the films. The obtained results show that the films are porous and composed of Ti(C_xN_{1 - x}), without apparent discontinuity in the interfaces adjacent to the titanium substrate. The thickness, ratios of C/N and pores sizes of the films tend to increase with the discharge time. When discharge-treated for 2.5 h, the film is about 15 μm thick and exhibits nanocrystalline characterization with grain size of 40-60 nm. Its hardness is Hv 2083 at the load of 0.2 N and the adhesion, Pc value, is more than 500 N. The formation process and mechanism of the Ti(C_xN_{1 - x}) films are discussed.