Characteristics and growth kinetics of plasma paste borided Cp-Ti and Ti6Al4V alloy

In the present study, CpTi and Ti6Al4V alloy were successfully plasma paste bonded using borax paste. The process was carried out in a dc plasma system at temperatures of 973, 1023 and 1073 K for 3,5 and 7 h in a gas mixture of 70% H-2-30% Ar under working pressure of 5 mbar. The properties of the boride layers were evaluated by scanning electron microscopy, X-ray diffraction and the micro-Knoop hardness tester. Growth kinetics of the titanium boride layers on the Cp-Ti and Ti6Al4V alloy were obtained by analyzing the experimental results and parameters including the thickness of boride layer, correspondent diffusion temperature and holding time. The presence of both TiB2 top-layer and TiB whisker sub-layer was confirmed by the X-ray diffraction and scanning electron microscopy techniques. The formation rate of the dual titanium boride layers was found to have a parabolic character at all applied process temperatures. The surface hardness of TiB2 layer ranged between 2077 and 2373 HK0.025. The activation energies of boron in Cp-Ti and Ti6Al4V alloys were calculated as 93.61 and 99.79 kJ.mol(-1), respectively depending on the temperature and layer thickness. (C) 2015 Elsevier B.V. All rights reserved.