Successful Binder Jetting of Titanium Alloys Appeals to the Modification of Surface Oxides: A Plasma Treatment Approach

Metal binder jetting (MBJ) offers great opportunities for fabricating high-strength titanium alloys for aerospace, medicine, and industrial applications. In this work, we studied the effect of particle size and surface energy on the dynamics of binder spreading and imbibition in Ti6Al4V powder beds by employing high-speed camera imaging and the Wilhelmy method. It is shown that binder imbibition in the titanium powder bed is significantly changed with the particle size due to geometrical-medicated wettability, capillary forces, and the surface oxide layers. Moreover, it is demonstrated that atmospheric pressure plasma processing of the powder particles can be used to modify the surface energy of particles, enhancing wettability. X-ray photoelectron spectroscopy shows that plasma treatment in nitrogen changes the type of surface oxide, thus improving the imbibition rate by an order of magnitude and the saturation rate by about 30%. The equilibrium saturation is also increased by about 15% Our results introduce a new strategy to enhance the processability of titanium powder for MBJ.