Suppression of metal surface oxidation during laser surface treatments

Inert cover gases (He, Ar and N 2 ) are commonly used to protect optical lenses, suppress plasma formation and inhibit metal surface oxidation during high power laser treatments. In the three examples studied, widely varying degrees of effectiveness have been found. A 20 lb inch −2 nozzle gas of Ar is found to be effective in prohibiting oxidation of polycrystalline Ni during surface melting with a continuous CO 2 laser. A CuAlFe alloy, however, oxidizes significantly under nearly identical conditions. It has been found that the redistribution of Hf, implanted in single crystal Ni and laser surface melted with Q‐switched Nd–YAG laser pulses, is sensitive to whether the laser melting is done in air or with a He cover gas. This, in spite of the fact that the melt time is less than 500 ns. We conclude that the use of an inert gas or very short laser pulses does not necessarily prohibit the gaseous ambient from reacting with metal surfaces during laser treatments.