Effect of electrolyte depletion on characteristics of anodic plasma electrolytic nitrocarburizing

Abstract

This article considers changes in the composition of aqueous electrolytes containing ammonia chloride and urea during plasma electrolytic nitrocarburizing of low carbon steels. The main purpose is the identification of the transport mechanism of nitrogen and carbon atoms movement from the urea into treated low carbon steel. The effect of changes in the composition of the electrolyte on treatment temperature and the structure of the modified layer was also evaluated. Urea decomposition to ammonia and carbon monoxide was confirmed. Electrolyte alkalization during treatment was found due to the action of the urea decomposi tion products. A hypothesis is proposed to explain the observed rise of the electrolyte surface tension near the vapor phase. This accounts for the observed increase in the sample temperature and in the electric current in the process of carburization. It is found that heating brings about an increase in thickness of the inner diffu sion layer, but the thickness of the surface nitrocarburized layer remains almost constant.

Plasma electrolytic saturation of steels with nitrogen and carbon

“…Change of electrolyte composition during PEN/C. Initial composition is 10% ammonium chloride and 15% carbamide [109].…”

Characterization of Nitrocarburized Coating by Plasma Electrolytic Saturation

“…Therefore, for fast modification of surface metals and alloys at very low temperatures, the plasma electrolytic process was used [8]. In a typical PEN/C process, an electrolyte containing carbon-rich and nitrogen-rich materials [9,10] is used while an additive [11] is added to improve the electrical conductivity of the electrolyte. Since the voltage in this process is very high, quenching the samples in electrolyte cause nitrogen and carbon atoms /free radicals to diffuse into the surface.…”