Research into the active species in nitriding plasmas has indicated that, c
ontrary to earlier assertions it is not ions bombarding the metal surface b
ut neutral particles, contained in the plasma, that are responsible for the
nitriding effect. Therefore, it is not necessary for the plasma to form di
rectly on the parts being treated. This important finding is the basis for
"through cage" (TC) or active-screen plasma nitriding, an approach claimed
to offer a number of advantages over conventional processing.