Nanosecond Pulses Improve Laser Nitriding

Nanosecond excimer laser pulses yield better results than femtosecond pulses when laser nitriding iron, according to a paper published in the Feb. 11 issue of Applied Physics Letters.

Laser nitriding exposes iron to a high-power-density laser in a nitrogen-laden atmosphere (right) to produce a micron-scale layer of iron nitride that increases surface hardness and protects against wear and corrosion.

Tests performed by the Universität Göttingen in Germany showed that nanosecond pulses yield better results during the process because they provide a thermal equilibrium and enough time for nitrogen to diffuse into a molten iron layer.

Femtosecond pulses apparently produce only a fallout of nitrogen from plasma that is formed above the metal. While the plasma and metal cool, this nitrogen forms a less-stable layer of amorphous or nanocrystalline iron nitride.