Study on laser removal mechanism and welding performance of TC4 titanium alloy oxide film

In response to the urgent need for efficient and green removal of the oxide layer on the surface of TC4 titanium alloy components of high-end equipment, this study used nanosecond pulsed laser removal technology to systematically evaluate the surface condition of the substrate after removing the oxide layer at different energy densities. The threshold range for complete removal was determined to be 3.34–3.76 J/cm², and it was found that the process can simultaneously achieve surface roughness optimization.When the oxide layer is not completely removed, the removal mechanism is mainly the thermal mechanism of laser ablation; when the oxide layer is completely removed, the removal mechanism is a composite mechanism of thermal shock, accompanied by plume eruption and plasma expansion explosion. More importantly, compared with the mechanical grinding samples, the laser-cleaned samples showed better mechanical properties at 3.76 J/cm², with a 15.2 % increase in microhardness and a 71.3 % decrease in wear rate. In addition, compared with not removing the oxide layer and removing the oxide layer by mechanical grinding, laser removal of the oxide layer can effectively suppress the porosity defects at the weld, and the tensile strength and elongation of the weld are also effectively improved, proving that laser cleaning can significantly improve the performance of the welded joint.