Corrosion behavior of titanium boride composite coating fabricated on commercially pure titanium in Ringer's solution for bioimplant applications

Abstract

The bonding of commercially pure titanium was performed at 850 degrees C, 910 degrees C, and 1050 degrees C for varied soaking periods (1,3 and 5 h) to enhance the surface properties desirable for bioimplant applications. The coating developed was characterized for the evolution of phases, microstructure and morphology, microhardness, and consequent corrosion behavior in the Ringer's solution. Formation of the TiB2 layer at the outermost surface followed by the TiB whiskers across the bonded CpTi is unveiled. Total thickness of the composite layer on the substrates bonded at 850, 910, and 1050 degrees C for 5 h was found to be 19.1, 26.4, and 18.2 mu m respectively which includes <3 mu m thick TiB2 layer. The presence of TiB2 phase was attributed to the high hardness similar to 2968 Hv(15) (gf) of the composite coating. The anodic polarization studies in the simulated body fluid unveiled a reduction in the pitting corrosion resistance after bonding the CpTi specimens. However, this value is >0.55 V-SCE (electro-chemical potential in in-vivo physiological environment) and hence remains within the safe region. Both the untreated and bonded CpTi specimens show two passive zones associated with different passivation current densities. Among the CpTi bonded at various times and temperatures, a 3 h treated shows better corrosion resistance. The corrosion of bonded CpTi occurred through the dissolution of TiB2. (C) 2014 Elsevier B.V. All rights reserved.