What Does Electron Beam Hardening (EBH) Mean?
Electron beam hardening is a material hardening process that uses an organized column of electrons as an energy source. The bombardment of the electron column on the material's surface creates heat, which is increased until the material or the surface of the material reaches a temperature at which its hardness is increased. This allows a material to have excellent surface wear resistance while still maintaining ductility and toughness in its core.
Corrosionpedia Explains Electron Beam Hardening (EBH)
Electron beam hardening is typically used to harden a very thin surface layer of an object by raising it to a specific temperature and then allowing it to cool rapidly.
What is unique about electron beam hardening over other hardening processes is that it is able to harden only the outermost layer of a material, leaving the core of the material with its original mechanical and chemical properties. Thicknesses of less than 0.004 inch (0.1 mm) can be hardened using the electron beam hardening process.
The thin surface layers of material that are affected by electron beam hardening are typically self-quenched. This means the ratio of the mass affected by electron beam hardening and the unaffected mass is small enough that the unaffected mass can cause the surface to cool fast enough to harden it.
Electron beam hardening involves exciting and emitting electrons from an electrode typically made of a tungsten or a tungsten alloy. To do this, thousands of volts are moved through the filament that then begins emitting electrons. During the electron beam hardening process, the emitted electrons are organized and focused using magnetic fields. This focusing gives the electron beam hardening process the energy density required to heat the material on which the work is being performed. The beam also needs to be directed across the part while the electron beam hardening process is being carried out, and this is done through a combination of moving the electron beam gun and more magnetic fields.
To avoid contamination of both the filament and the material undergoing the electron beam hardening process, all of the work being performed is done in a vacuum.