Cathodic Boronitrocarburising and Anodic Polishing of Mild Steel 20 in Electrolitic Plasma

Abstract

The paper discusses a possibility of increasing the wear and corrosion resistance of a low carbon steel surface after cathodic plasma electrolytic boronitrocarburising in a solution of boric acid, glycerin, and ammonium chloride, with the subsequent anodic plasma electrolytic polishing in an ammonium sulfate solution due to the formation of a modified structure consisting of a dense oxide layer and a diffusion layer below it, which contains up to 0.87% carbon, 0.80% nitrogen, and 0.87% boron upon reaching microhardness up to 970±20 HV. The competitive influence of the surface erosion under the action of discharges and high-temperature oxidation on the morphology and roughness of the surface is revealed. A positive effect of reducing the surface roughness during the formation of a dense oxide layer on the surface and a hardened diffusion layer under it on reducing the friction coefficient and mass wear, as well as reducing the roughness and additional oxidation of the surface during polishing on reducing the corrosion current density, has been established.