Application of Direct Current Plasma Sintering Process in Powder Metallurgy

Abstract

Direct current (dc) plasma-assisted sintering of metal parts is a promising and relatively new research and development field in powder metallurgy (PM). In the present entry, it is intended to introduce the reader to the main applications of the dc plasma sintering process in PM. To achieve this goal, the present entry is divided in a brief introduction and sections in which the bases of the dc plasma abnormal glow discharge regime and its influence in the sintering process are carefully treated. In this case, a clear language is purposely used to didactically introduce the reader to this "fascinating glow world", the dc plasma-assisted sintering of metal parts, aiming to put in evidence the main points on physicochemical aspects of the plasma environment, basic knowledge of the plasma heating, and surface-related phenomena during dc plasma sintering of parts.All these aspects are treated considering the main techniques of the dc plasma-assisted sintering process applied to PM. Finally, some results on DC plasma heating, sintering and surface modification are presented.

Surface state change influence’s theoretical approach of pressed iron on hollow cathode discharge characteristics: first results of plasma heating reproducibility for sintering purposes

“…It is to be remembered that in plasma processing, the sputtering effect caused by the plasma fast-species bombardment becomes especially important in terms of sintering mechanisms [34], since it leads the density of sputtered metal atoms to be increased in the plasma phase, thus acting directly on the enhancement of the evaporation and recondensation mechanism. As presented in [34], the superficial diffusion mechanism tends to be strongly incremented by the fast-species bombardment, the same also occurring for the volume diffusion mechanism, since the vacancy density next to the surface tends to be increased as a result of one of the possible events of the plasma-surface (interface) interaction [35].…”

“…Plasma sintering of metallic components can also be carried out from glow discharges working in the abnormal regime of the current-voltage characteristic of a dc (direct current) electrical discharge, normally using gas mixtures containing hydrogen and argon [29][30][31][32][33][34]. In the abnormal regime [35], the cathode surface, thus the parts under sintering, is fully covered by the glow region (or the plasma itself), guaranteeing the condition needed to achieve uniform treatment.…”