Chemical surface finishing of electron beam melted Ti6Al4V using HF-HNO3 solutions

Electron Beam Melting is an Additive Manufacturing technology that allows the production of items using metal powder as raw material. The main advantage of Additive Manufacturing (AM) is realizing complex shape components; however one of the main defects is the poor quality of the surface. To this aim, different post processing treatments have been proposed such as machining, surface laser melting, sand blasting, etc. The main drawback of these technologies is the necessity to use tools that makes complex shape item difficult to handle. This inconvenient does not occur in chemical machining, since a chemical solution can operate in an undifferentiated way on the whole surface of a component. In this work some components in Ti6Al4V obtained through AM have been treated in acidic solutions containing HF and HNO3 with different HF/HNO3 molar ratio. All the solutions employed have proven to be effective in smoothing the metal surface, but the best results have been obtained with solutions with high content of HNO3. It should be noted that the process causes changes in the surface composition with respect to the received samples with an impoverishment of Al. This effect is partially mitigated by the passivating action of HNO3.