Microstructure and corrosion behavior of porous coatings on titanium alloy by vacuum‐brazed method

The microstructural evolution and electrochemical characteristics of brazed porous‐coated Ti‐6Al‐4V alloy were analyzed and compared with respect to the conventionally 1300°C sintering method. The titanium filler metal of low‐melting‐point (934°C) Ti‐15Cu‐15Ni was used to braze commercially pure (CP) titanium beads onto the substrate of Ti‐6Al‐4V alloy at 970°C for 2 and 8 h. Optical microscopy, scanning and transmission electron microscopy, and X‐ray diffractometry (XRD) were used to characterize the microstructure and phase of the brazed metal; also, the potentiostat was used for corrosion study. Experimental results indicate that the bead/substrate contact interface of the 970°C brazed specimens show larger contact area and higher radius curvature in comparison with 1300°C sintering method. The microstructure of brazed specimens shows the Widmanstätten structure in the brazed zone and equiaxed α plus intergranular β in the Ti‐6Al‐4V substrate. The intermetallic Ti 2 Ni phase existing in the prior filler metal diminishes, while the Ti 2 Cu phase can be identified for the substrate at 970 for 2 h, but the latter phase decrease with time. In Hank's solution at 37°C, the corrosion rates of the 1300°C sintering and the 970°C brazed samples are similar at corrosion potential ( E corr ) in potentiodynamic test, and the value of E corr for the brazed sample is noble to the sintering samples. The current densities of the brazed specimens do not exceed 100 μA/cm 2 at 3.5 V (SCE). These results suggest that the vacuum‐brazed method exhibits the potentiality to manufacture the porous‐coated specimens for biomedical application. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006