A fundamental contribution to a study of the active screen plasma nitriding process

Abstract

Active Screen Plasma Nitriding (ASPN) is a novel plasma based nitriding process which challenges many of the existing hypotheses concerning mass transfer in plasma nitriding and, in turn, questions the influence of substrate bias during nitriding. In this study, a Field Emission Gun Scanning Electron Microscope analysis was used to investigate material transfer from the active screen. The results demonstrate that material transfer and deposition, in the form of nano-particles, take place from the active screen to parts that are in a direct line of sight of the active screen. The nano-particle distribution is significantly influenced by the type of active screen material used and the application of substrate bias. However, the suggestion that the mechanism of mass transfer in ASPN is directly related to sputtering of material from the active screen is questioned by the observation that AISI H13 steel samples treated in a non line of sight position in the ASPN chamber showed a significantly higher nitriding response than AISI H13 samples treated in direct line of sight of the active screen.