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

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.