The first historical example of laser hardening application in production, dates back to 1973 and was developed by the car industry: since then this type of surface process has been tested to various extents, although it did not meet the initial forecasts of massive industrial boom. Laser hardening is a process by which the characteristics of a thin surface layer are modified, without using external hardening systems, as a consequence of fast heating above austenitisation temperature followed by fast cooling to allow the formation of martensite. The power density is set in order to allow a certain depth of treatment without any surface melting, which is however possible according to requirements. From a metallurgic point of view, the resultant microstructure is particularly thin, and subsequently very hard but still tough, but the main advantage lies in the selectivity of the treatment, characterised by low heat input and reduced distortion.