Nitridation of iron by CW-CO2 laser nitriding technologies

Laser nitriding is an attractive method to improve metal surface properties, such as hardness, wear, and corrosion resistance, with the advantage of simple experimental setup, rapid treatment, and precise process control. Here, iron nitride (FexN) is obtained by the mixing technology with laser and pre-heated nitrogen (LHN) or nitrogen plasma (LPN) beams on the surface of pure iron in atmosphere ambient. In these two technologies, laser provides heat, pre-heated nitrogen provides help for nitrogen activity, and nitrogen plasma provides nitrogen ions, respectively. The two technologies are superior to the previous laser nitriding (LN) methods. However, iron nitride more difficult was obtained by the mixing technology with laser and pre-heated nitrogen than by the mixing technology with laser and plasma, and iron oxide was not observed in the sample treated by the latter. The feasibility of the technologies is analyzed in theory. X-ray diffraction measurements reveal formation of iron nitride in the as-treated sample by these technologies. Moreover, the concentration and phase formation of iron nitride were given at different laser power densities and different scanning velocities with emphasis on the mixing technology with laser and plasma.