Research on the removal mechanism of surface oxide film and enhanced weld performance on Ti-6Al-4V alloy

The natural oxide film on the surface of titanium alloy is very harmful to its subsequent welding performance. In this work, the oxide film on the surface of Ti-6Al-4V alloy was removed using grinding and pulsed laser cleaning as pre-welding treatments. The results reveal that both the laser cleaning and grinding can significantly reduce the oxygen content on the surface of Ti-6Al-4V alloy, with the oxygen content being only 2.53% under optimised laser process. The composition ratio at this moment is 11.83% TiO, 41.51% Ti2O3, 27.51% TiO₂ and 19.15% Ti. An appropriate cleaning power (50W) can make the surface less prone to cracking. It has been also found that laser cleaning can reduce the porosity to 1.93% in the joint and increase its tensile strength to 1032.68 MPa, 109.22% of that of the untreated joint. Laser cleaning is an alternative method for obtaining high welding performance, which can be widely applied to the manufacturing field.