A surface treatment used to harden or clad surfaces of ferrous metals. For hardening, a laser beam with a high power density heats a small area on the surface of the workpiece, causing changes to the atoms in the lattice of the material (austenite). As the beam moves away, to another spot on the surface, the heated area is rapidly cooled by the surrounding metal (self-quenching). This rapid cooling stops the lattice from returning to its original arrangement, resulting in a very hard surface structure (martensite). For cladding, the high temperature of the laser helps bond tracks of injected powder with the surface of the workpiece.