Abstract:Highly preferred orientation TiB2 coatings were obtained by electrochemical techniques of continuous current plating (CCP) and pulse current plating (PCP) in fluoride-chloride electrolytes (KF-KCl) containing K2TiF6 and KBF4 as the electrochemically-active components. The effects of cathode current density on the crystal size, preferred orientation, micro stresses and lattice constants were studied by X-ray diffraction (XRD). The results indicate that the crystal size gets smaller with the increase of the cathode current density due to the increase of the nucleation rate at the over-potential. Compared with the CCP, the crystal size of TiB2 coatings prepared by PIC is finer because PIC can weaken the concentration polarization and increase the nucleation rate by increasing the ion concentration of diffusion layer. The preferred orientation of TiB2 coatings prepared above is (001) plane at the experimental conditions, which can be well explained by the two-dimension crystal nuclei theory. The lattice constant of TiB2 coatings deviates from the theoretical value due to the stress in coatings. Besides, it is confirmed that the binding between TiB2 coatings and graphite substrates is the physical binding from the results of thermodynamic predictions, XRD and EDS (Energy Dispersive X-ray Spectrum). The existence of some cracks at the interface may be attributed to the difference between the thermal expansion coefficients of TiB2 and graphite.