Studies on the effect of process parameter on corrosion behaviour of electron beam welded Ti-based alloy (Ti6Al4V)

The present work concerns understanding the effect of process parameters on the corrosion behavior (in a 3.56 wt.% NaCl Solution) of electron beam welded Ti6Al4V developed with an acceleration voltage of 60 kV, beam current varying from 42–48 mA, and welding speed ranging from 800–1000 mm/min. In addition, beam oscillation (1–2 mm) was employed for the samples processed with an applied voltage of 900 mm/min and beam current of 45 mA. Electron beam welding leads to the formation of defect-free welding with the presence of α, α' martensite, and a few β phases in the microstructure. A detailed electron backscattered diffraction study shows that the area fractions of low/high angle grain boundaries vary with process parameters. The average Kernal misorientation angle of the electron beam welded samples varies from 0.49°-0.57° as compared to 0.40° for as-received Ti6Al4V. Potentiodynamic polarization study in a 3.5 wt.% NaCl solution shows a superior corrosion resistance for the samples welded with beam oscillation as compared to the case without any oscillation. Electrochemical impedance spectroscopy measurement reveals the formation of a complex passivating film on the oxide surface. The X-ray photoelectron spectroscopy (XPS) analysis of the post-corroded samples shows the presence of titanium oxide (rutile and anatase) on the surface in the case of electron beam welded samples as compared to only anatase in as-received Ti6Al4V.