The high-power heat source produced by a laser beam is ideally suited for surface modification. Laser heating produces local changes of the surface of the material while leaving intact the properties of most of the particular components. The main laser surface engineering applications can be broken down into three main areas (Figure 1). The following processes may also be divided into those depending on metallurgical changes in the surface of the bulk material i.e., transformation hardening, annealing, grain refining, glazing and shock hardening, and those involving a chemical modification to the surface by addition of new material i.e., alloying and cladding.

• Heating without melting is commonly known as heat treatment. This involves solid-state transformation, so that surface of the metal is not melted. The portion of the beam power absorbed by the material is controlled by the absorption of the surface of the material. Both mechanical (hardness, abrasion, resistance etc.) and chemical properties, (corrosion resistance etc.) can frequently be greatly improved by the metallurgical reactions produced during these heating and cooling cycles (Figure 2) ;
• Heating with melting, i.e., laser glazing, surface homogenization, remelting. This method produces very fast heating, melting and cooling for changing surface properties;
• Melting with addition of material, i.e., cladding, alloying impregnation, involves melting of the surface plus material added to the surface to form a modified surface layer (Figure 3).