# Effect of Electropolishing on the Microstructure and Tribological Properties of Electrolyte-Plasma Borided Layers on 30KhGSA Steel

## TL;DR

This study shows how polishing improves the durability and smoothness of a special treatment on steel, making it better for high-stress applications.

## Contribution

The novel contribution is demonstrating the combined effect of plasma-electrolytic boriding and polishing on steel's wear resistance and surface quality.

## Key findings

- Plasma-electrolytic boriding increases microhardness up to 1500–1600 HV0.1, 5–6 times higher than untreated steel.
- Plasma-electrolytic polishing reduces surface roughness by nearly an order of magnitude and decreases wear rate by almost half.
- The combined treatment significantly lowers friction coefficient and improves steel performance under high loads.

## Abstract

The study investigates the effect of plasma-electrolytic polishing on the structure and wear resistance of 30KhGSA steel after plasma-electrolytic boriding. Plasma-electrolytic boriding was carried out in a boron-containing electrolyte at a temperature of 900 °C, which ensured the formation of a hardened modified layer consisting of a surface oxide layer, a subsequent zone composed of boride phases FeB and Fe2B, as well as a transitional martensitic zone. To remove brittle oxide phases and reduce surface roughness, plasma-electrolytic polishing in an alkaline solution was applied, which made it possible to form a smoother and more stable surface. The results showed that plasma-electrolytic boriding increases the microhardness up to 1500–1600 HV0.1, which is 5–6 times higher compared to untreated steel, and reduces the friction coefficient and wear rate. However, the borided layers exhibit brittleness and surface roughness. Subsequent plasma-electrolytic polishing made it possible to reduce surface roughness by nearly an order of magnitude, decrease the friction coefficient by more than 30%, and almost halve the wear rate. The obtained results confirm the high potential of this combined technology for strengthening structural steel components operating under high loads and severe wear conditions.