Most metals could be laser etched, marked, cut and welded, metals can be directly lasered by fiber lasers, whereas laser inks needed for metal marking by Co2 lasers, high power Co2 laser can be used for metal cutting directly, high power diode laser normally used for metal alloy welding.
Color changing appears when laser beam heat the metal surface and form oxide layer, the color called tempering color and depends on the temperature of heated area, starting from 350˚F (176˚C) light yellow, to 500˚F (260˚C) brown and 590˚F (310˚C) deep blue, the latest MOPA fiber laser gives up to 32 colors to ferrous metals.
Stainless steel annealing marking and anodized aluminum black marking is a type of color marking.
The work piece surface remains even after color marking because nothing added to or removed from it.
Metal surface vaporized by the laser beam and removed by exhaust fans in this application, deep marking effects can be made by repeatedly laser the same area.
The laser focal point is small, only the area close to focal point can be engraved due to the energy delivered by the laser not strong enough to change metal layers away from focal point, normally up to 50 µm depth can be engraved in the metal surface.
Since the material gets simultaneously heated and reacts with air, there is often a discoloration at the engraving areas, this is more distinctly when using laser marking machine.