Nitriding with ion beam from Hall-type source

The nitrogen ion beam produced by a Hall-type ion source has been used for the nitriding of 34CrMo4 steel, in order to evaluate the potential of this device for surface processing. This compact device combines an ion source a nd an accelerator. It provides a high ion current density because the ion s pace charge is neutralized by the closed cycle electron drift. The ion ener gy at the exit of the discharge channel is close to the discharge voltage. The nitriding was performed at two temperatures: 570 degrees C and 350 degr ees C. The duration of the nitriding was 4 h in the first case and 8 h in t he second one. At 350 degrees C the compound layer was 2-3 mu m thick and t he diffusion zone was 150 mu m thick. The maximum hardness on the surface i s 670 HV0.05, The results indicate that this method allows nitriding at low er pressure and sample temperature than the conventional ones. The method a ppears to be highly directional. (C) 1999 Elsevier Science B.V. All rights reserved.