Thermionic Electron Emission of the Tungsten Electrode
Thermionic electron emission describes the exit of electrons from the glowing tungsten electrode during TIG welding, which is facilitated by thermal excitation above the work function. Doping with rare earths significantly lowers this work function.
In TIG welding, the heat causes the tungsten electrode to emit electrons. To keep the arc stable, substances like thorium or cerium are added to the tungsten. They lower the work function, meaning electrons are released more easily from the material. If electron emission is off, you'll notice it by an unstable arc or poor weld bead formation. That's usually due to the wrong electrode type or an overheated, contaminated electrode tip. So make sure to use the right electrode for your application and keep the tip clean and properly ground.