Surface hardening using laser beams.
The surface of the workpiece is is heated up to austenitization temperature at a temperature increase rate of > 1000 K/sec. This process is performed in a controlled manner until the melting point is approached but not actually reached. The hold time may range between 10-3 to 10 sec. The cooling rate defined by the heat dissipation into the workpiece; Normally, the process takes place under atmospheric conditions. The workpiece and casting areas underneath the surface remain cold so that self-hardening of the surface occurs without the need for quenching. For this reason, hardnessdistortion (see Hardness stress) is largely prevented; And what is more, reworking is generally not required.
The thin oxide layer that forms through the process is insignificant and can be easily removed uppon requirement. In contrast to other hardening methods (s. Hardening), with laser hardening the structure is considerably more fine-grained, the hardness values are in the upper range of hardnesses that can be achieved through martensite formation. The maximum hardness depths that can be achieved depend on the material and may reach up to 1.5 mm.
Video 1:Laser hardening, source ALOtec GmbH, Dresden
Electron beam hardening