Pulsed CO2lasers for the surface heating and melting of metals

We explore the possibilities of using pulsed electron-beam-excited CO
2
lasers for the generation of metal surfaces with improved properties through surface alloying or microsecond melting and thermal-conductance quenching (self quenching). Air plasma ignition yields enhanced thermal coupling to highly reflective metals, but is shown nevertheless to prohibit the melting of metals with lasers of reasonable size. Suppression of the air plasma by evacuation leads not only to unimpaired metal heating but to a new and little-understood mode of enhanced thermal coupling, with highly favorable characteristics. The surface melting of even refractory metals with single microsecond-duration pulses should be possible with pulsed CO
2
lasers of modest size.