Comparison of compound layer nucleation mechanisms in plasma nitriding and nitrocarburizing: the effect of CHn species

Abstract

This article presents a new study of the mechanisms of plasma nitriding and nitrocarburizing processes, with particular emphasis on plasma diagnostics and light element detection at the treated sample surface. The results indicate that in the nitriding process neutrals, such as Fe, N and ions (such as N⁺), are abundantly present near the cathode region, suggesting that the formation of iron nitrides occurs through the combination of these species. Light element detection by elastic recoil analysis (ERA) shows that hydrogen is not present on the nitrided surface, but it is abundant on the nitrocarburized surface. The latter result is discussed in view of existing nitriding models. The role of CH_n radicals in plasma nitrocarburizing is also discussed.