The influence of bias and in-situ cleaning on Through Cage (TC) or Active Screen Plasma Nitrided (ASPN) steels

Abstract

The effect of a substrate bias and prenitride plasma etching on the nitriding response of four steel substrates is investigated in a two factor two level full factorial experimental design. The steels investigated were P20 (M200, Plastic mould steel), H13 (W302, Hot-work tool steel, as received), 4140 (Preheat treated nitriding steel) and 1020 (CS1020, Bright mild steel). The nitriding response was determined from surface and cross-sectional hardness measurements. Nitrogen depth profile measurements were obtained using Glow Discharge Optical Emission Spectroscopy. — Considering the main effects, the results show that without worktable bias during the nitriding step there is effectively little or no nitriding response in most of the materials. The prenitride plasma etch did not produce a significant surface hardness response in all steels except H13, where a prior etch substantially increased surface hardness and influenced the hardness depth profile. The bias significantly increased the nitrogen wt%. The plasma etch also influenced the near surface nitrogen wt% concentrations, however, the practical implications of this require further investigation.