Laser surface alloying

Techniques based on high power lasers, which modify the chemical composition of the microstructure of the surface of a material in order to improve some of its properties are considered in terms of solving both the high melting point and segregation problems in the fabrication of metal and ceramic alloys. Application of these lasers in such materials processing areas as deep penetration autogeneous welding, cutting, drilling, transformation hardening, and experimental shock hardening is discussed. It is shown that the high power densities that lasers can produce, equivalent to thermal sources of temperature above 20,000 C, facilitate the melting of all phases of the alloy. Furthermore, the high power density of lasers allows melting to be localized at the surface, with negligible subsurface heating, thereby establishing high cooling rates. In this process, laser glazing, the extremely rapid chill rates of thin molten zones produce extremely homogeneous metallurgical microstructures, including amorphous alloys, the ultimate in alloy homogeneity.