Journal of Materials Research and Technology Journal of Materials Research and Technology
J Mater Res Technol 2017;6:251-7 DOI: 10.1016/j.jmrt.2017.05.003
Original Article
Corrosion resistance of Ti-6Al-4V and ASTM F75 alloys processed by electron beam melting
E. Almanzaa,, , M.J. Péreza, N.A. Rodrígueza, L.E. Murrb
a Departamento de Metal-Mecánica, Instituto Tecnológico de Saltillo, Saltillo Coahuila, México
b Department of Metallurgical Materials and Biomedical Engineering, University of Texas at El Paso, El Paso, USA
Received 13 October 2016, Accepted 08 May 2017
Abstract

The electron beam melting (EBM) is a useful technique for fabricating alloys that are difficult to machine and require expensive tools as well as the presence of inert atmosphere for further treatments. Under vacuum, EBM provides a controlled environment, reducing the drawbacks of the alloys of their processing in a conventional manner and thereby improving their microstructure, which can enhance corrosion resistance. In the present work, the corrosion resistance of the Ti-6Al-4V and ASTM F75 alloys was evaluated by using the Tafel extrapolation technique with scan rates of 0.05, 0.1 and 0.166mV/s. The corrosion specimens were submerged in a Hank solution to simulate the corporal fluid. The specimens were characterized before and after the corrosion tests by optical microscopy and scanning electron microscopy, as well as a chemical microanalysis by EDS. The microstructural characterization before the corrosion tests revealed a dual phase (α+β) microstructure and α′ martensite in the Ti-6Al-4V alloy. For the ASTM F75 (Co-base) alloy, carbides were observed on the grain boundaries. Corrosion resistance increased in the Ti-6Al-4V alloy, from 0.50 to 0.14mpy, possibly due to the formation of a TiO2 passive layer. For the case of the ASTM F75 alloy, the corrosion rate decreased from 0.21 to 0.14 milli-inches/year (mpy) due to the formation of Cr layer. The corrosion results were observed to be very similar for the EBM fabricated alloys in comparison with more commercially fabricated alloys.

Keywords
Electron beam melting, Passive layer, Tafel extrapolation
J Mater Res Technol 2017;6:251-7 DOI: 10.1016/j.jmrt.2017.05.003