The effect of plasma nitriding treatment time on the tribological properties of the AISI H13 tool steel

摘要

In a conventional plasma nitriding mechanism and actual processing, the sample is primarily treated with mtrogen ions. Hence, nitriding is not mainly performed using neutral nitrogen species, such as nitrogen atoms. In this study, a novel method to control nitrogen ions was implemented, and nitriding of the AISI H13 tool steel was performed in electron-beam-excited plasma using neutral nitrogen species and nitrogen ions. The effect of various treatment times on the formation of a hard but brittle compound layer were investigated, along with subsequent tribological change to the surface of the material. The results show that tool steel nitrided by neutral nitrogen species for 6 h produced a diffusion-based nitrided layer (up to 60 mu m) without altering the pretreatment surface finish (R-a = 14 nm), and there was a specific wear rate of less than one hundredth (4.3 x 10(-7) mm(3)/N-m) compared with the untreated sample (2.9 x 10(-5) mm(3)/N.m). Conversely, nitriding by ions produced a rough, brittle compound layer on the surface of the tool steel. The samples with a compound layer exhibited a lower coefficient of friction than those with no compound layer.