Spectroscopic investigation of plasma electrolytic borocarburizing on q235 low-carbon steel

Highlights: • The plasma discharge behaviors for PEB/C on steels were evaluated by OES. • Electron temperature, concentration, atomic ionization degree were calculated. • The decomposition mechanism of electrolyte and was analyzed. - Abstract: A plasma electrolytic borocarburizing process (PEB/C) in borax electrolyte with glycerin additive was employed to fabricate a hardening layer on Q235 low-carbon steel. Optical emission spectroscopy (OES) was utilized to investigate the spectroscopy characteristics of plasma discharge around the steel during PEB/C process. Some plasma parameters were calculated in terms of OES. The electron temperature and electron concentration in plasma discharge zone is about 3000–12,000 K and 2 × 10²² m⁻³–1.4 × 10²³ m⁻³. The atomic ionization degrees of iron, carbon and boron are 10⁻¹⁶–10⁻³, and 10⁻²³–10⁻⁶, 10⁻¹⁹–10⁻⁴, respectively, which depend on discharge time. The surface morphology and cross-sectional microstructure of PEB/C hardening layer were observed, and the electrolyte decomposition and plasma discharge behaviors were discussed