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 and an accelerator. It provides a high ion current density because the ion space charge is neutralized by the closed cycle electron drift. The ion energy at the exit of the discharge channel is close to the discharge voltage. The nitriding was performed at two temperatures: 5708C and 3508C. The duration of the nitriding was 4 h in the first case and 8 h in the second one. At 3508C the compound layer was 2–3 mm thick and the diffusion zone was 150 mm thick. The maximum hardness on the surface is 670 HV0.05. The results indicate that this method allows nitriding at lower pressure and sample temperature than the conventional ones. The method appears to be highly directional. q1999 Elsevier Science B.V. All rights reserved.