Features of nitroquenching of medium-carbon steel during anodic electrolyte–plasma processing

Abstract

The research described in this paper is devoted to short-term anodic nitriding of grade 45 steel with postquenching (nitroquenching) in the aqueous solution of ammonia and ammonia chloride. The modified layer structure, as revealed, is composed of alternate layers: a surface oxide layer composed of FeO and Fe₃O₄; a layer of dispersed nitrides Fe₄N and Fe_2–3N with retained austenite; next, a martensitic zone composed of nitrogen and carbon; and the initial nitrogen-enriched ferrite–pearlitic structure. It is found that concentrations of electrolyte components and processing conditions affect the formation character and properties of diffusion layers. The possibility is shown for obtaining a nitroquenched layer 130 µm in thickness with a surface microhardness of to 1200 HV with a decrease in roughness R_a from 0.57 to 0.55 µm, R_z from 1.75 to 1.62 µm, and R_max from 5.74 to 4.00 µm.