The Advancement of Ultrasonic Metal Welding Tool Materials
By Matt Bloss on Thursday, June 24th, 2010
Ultrasonic Metal Welding is a unique process that has typically been limited to applications involving softer, high conductivity alloys. Skipping over the physics and metallurgy of the process; let’s just say that high-frequency vibrations are transferred to the work pieces via a set of ultrasonic tools to create a solid-state bond. For welding softer materials, like aluminum and copper, these ultrasonic tools are typically made of hardened tool steel. However, it has been found over and over that it is also possible to ultrasonically weld higher-strength alloys, including Stainless Steel, Titanium Alloys, Nickel-based superalloys, Advanced High Strength Steels, and Molybdenum, to mention a few. The catch (there is always a catch) is that the ultrasonic tools can be limited to a single weld before failure, which could get costly if one desired to make more than one weld. The challenge is that many of these alloys are similar, if not stronger than, the ultrasonic tools being used to weld them.
To combat this challenge, our Ultrasonic group peered over the cubicle walls and “borrowed” some tool materials from the Friction Stir group at EWI. Friction-Stir and Ultrasonic are somewhat similar in that both are solid-state processes that involve plastic deformation of the materials being welded via a welding tool. During experiments with various tungsten-based ultrasonic welding tools, many repetitive welds were possible in 0.5mm thick Stainless Steel, Titanium, and Nickel-based Superalloys.