Effect of carbon and nitrogen diffusion zone on growth mechanism of boride layer produced on Q235 Steel

Abstract

The purpose of this study was to indicate the effect of the presence of the carbon and nitrogen diffusion zone below the boride layers of Q235 low-carbon steel. The boride layers were produced by cathodic plasma electrolysis treatment (PET). Based on the results, the boride layer thickness on the treated samples at 260 V and 300 V varied from 10 μm to 22 μm. The XRD and GDOES analysis demonstrate that the boride layer on the treated samples mainly consists of single Fe 2 B phase, and the top loose layer mainly contain Fe 2 O 3 , Fe 3 C, Fe 4 N, and BN phases. The boride layers exhibited excellent scratch resistance compared to the bare Q235 steel. In addition, the plasma electron temperature was around 3000–4500 K, and the frequency spectra of acoustic signals were related to the voltage-time and current-time curves. At the high temperature and strong electric field, the decomposition reaction of electrolyte and the growth mechanism of the boride layers were discussed. Schematic of reactions in vapor gaseous envelope around the Q235 steel cathode during the plasma electrolysis process. • The boride layers on Q235 steel were produced by cathodic plasma electrolysis treatment. • The boride layers exhibited excellent scratch and adhesion resistance. • The OES and air acoustic spectra were measured. • Decomposition reactions of electrolyte and growth mechanism of boride layer were discussed.