Insights on the pulsed-DC powder-pack boriding process: The role of the electric charge on the growth of the boride layer and the semiconductor behavior of the boriding media

In pursuit of innovating the conventional powder-pack boriding (CPB) process by introducing an electrical driving force, novel findings regarding the kinetics growth of boride layers produced on an AISI 8620 steel through the pulsed-DC powder-pack boriding process (PDCPB) were obtained. The PDCPB accelerates B diffusion on the surface of the specimen, resulting in an augmentation of the growth kinetics around 12 % and 15 % for FeB and Fe2B, respectively, compared to those observed in the CPB process. Additionally, the effect of polarity inversion half-cycles on the growth of the FeB-Fe2B layer during the PDCPB was studied. The experiments were conducted at temperatures of 850 °C, 900 °C, and 950 °C, with different exposure times, and polarity inversion half-cycles of 30 s and 50 s, maintaining a constant current density of around 177 mA cm−2. An estimation of the electric charge (q) using a transfer function considering minimal and maximum temperatures was achieved. It was confirmed that, with a symmetrical inversion, q was similar for both 30 s and 50 s polarity inversion half-cycles, indicating no influence on the growth kinetics of the boride layers. •Each component of boriding media influenced its electrical behavior during PDCPB.•A holistic explanation of the boriding media electrical behavior was developed.•Transfer function was used for the estimation of electric charge during PDCPB.•Similar electric charge was obtained for half-cycles >7 ms.•Electric charge did not influence the boride layer growth kinetics.