Principles, mechanisms and applications of active screen plasma nitriding

Notwithstanding its rapid development and numerous advantages over traditional nitriding methods, the uptake of plasma nitriding technology into industrial surface engineering has slowed down recently. Contributory drawbacks in conventional DC plasma processing, such as difficulties in maintaining a uniform chamber temperature, particularly with full workloads, damage caused to parts by arcing, and the edging and hollow-cathode effects, are countered by active screen plasma nitriding. This method is based on the finding that, contrary to earlier assertions, it is not ions bombarding the metal surface that are responsible for the nitriding effect and, therefore, it is not necessary for the plasma to form directly on the parts as in DC plasma nitriding. The mechanism of nitrogen mass transfer in active screen nitriding has been investigated, and a modified sputtering and deposition model has been proposed to explain the results.