Development of Fill Impact Welding technique for metal additive manufacturing

Abstract

Metal additive manufacturing typically utilizes powder as feed. Fill impact welding, uses dime-sized pieces of sheet metal launched at high speeds to impact and weld to the metallic substrate. The driving force can be generated by several means, including vaporizing foil actuators used in this work. A custom impact welding fixture was built to launch 0.5 mm thick and 6.35 mm diameter flat circular metallic disks (flyers) to speeds greater than 500 m/s over a travel distance of 5 millimeters. The flyers impacted target plates placed at fixed relative angles. Fully welded interfaces were observed via cross sectional metallography as well as non-destructive evaluation methods of ultrasonic testing. It was demonstrated that titanium flyers can be reproducibly welded to copper for a certain set of parameters. Furthermore, the impact velocity was found to be controllable and repeatable for various input energies from the capacitor bank power system. For example, for 2.0kJ input energy shots, the average peak velocities of the flyer were measured to be 800 m/s with a variation of less than 3%.