If you need a moment of Zen, I suggest pouring a glass of your favorite adult beverage, queuing up an ASMR clip, and watching this slow-motion video of linear friction titanium welding. What starts out as two pieces of shiny, silver, but otherwise featureless metal rubbing against each other soon turns into a magical ballet of arcs and sparks before resolving into a horizon of molten titanium. It’s beautiful. But what’s going on here?
TWI, a company that pioneered linear friction welding, defines the solid-state joining process as one that “involves two parts being pushed together, one oscillating at a high frequency.” In other words, one piece is stationary while another rubs back and forth against it at high speed. This results in friction that builds up enough heat to raise the metals to a temperature at which they can fuse. When the oscillation is stopped, the metal cools, and the result is a “forged-quality weld.”
Though this process can be done in as little as one second, the one-minute video above has been slowed down considerably so that we might enjoy the magical display that would otherwise be lost in the blink of an eye. The sparks you see dancing across the screen could be impurities within the metal or incandescent bits of molten titanium itself that bubble up during the intense heating process. Titanium melts at 1,677°C (3,051°F) but since the metal is not melted but fused, this is actually more of a forging technique as temperatures reach between 600°C and 1200°C. Once the “Dance of the Sparks” has concluded, a wave of flowing titanium cools down from a cherry-red color as the pieces fuse together, leaving a build-up of metal–known as flash–along the sides of the interface.
Linear friction welding is certainly useful for a number of industrial processes, but in slow motion, it’s also quite beautiful.
Images: TWI, MTI Welding