Growth kinetics of titanium borides produced by CRTD-Bor method

In this study, a new boriding method called CRTD-Bor (Cathodic Reduction and Thermal Diffusion based boriding) was applied to titanium in a systematic manner and the effects of boriding process parameters on the morphological and chemical state of boride layers were explored. The presence of both TiB and TiB₂ phases was confirmed by the X-ray diffraction technique. The cross-sectional examination of borided titanium verified the boride layers consisted of a homogeneous TiB₂ phase on the top and TiB whiskers toward the substrate. Moreover, the growth kinetics of the TiB₂ layers forming on titanium substrates was investigated during CRTD-bor which was performed at a constant current density of 200mA/cm² in a borax based electrolyte at temperatures ranging from 900 to 1100°C for periods of 15 to 120min. The rate of the TiB₂ layer formation was found to have a parabolic character at all applied process temperatures. The activation energy (Q) and the pre-exponential factor (K_o) of the TiB₂ layer were determined as 189.9kJ/mol and 4.66×10^-7m²s^-1, respectively. The specific empirical equation that can be used to estimate the thickness of the TiB₂ layers (d_TiB2) for the conditions explored in the study is dTiB2=682.67exp-22833/Tt1173K≤T≤1373K;200mA/cm2.