An experimental and modelling study on pulse current integrated CRTD-Bor process

In this study, pulse current integrated cathodic reduction and thermal diffusion-based boriding (PC/CRTD-Bor) process was applied to low carbon steels to grow industrially preferred single phase Fe₂B layers in short durations (<1 h). For this purpose, the determination of combined effects of duty cycle and current density were examined at two sets of experiments as follows: (I) Duty cycle investigations where the specimens were borided at the constant current density of 200 mA/cm² for different duty cycles (i.e., 1/8 - 1 s reduction & 7 s diffusion to 1/2 - 1 s reduction & 1 s diffusion) and (II) current density investigations where boriding trials were carried out at the constant duty cycle of 1/4 for different current densities (e.g., 50 mA/cm² to 700 mA/cm²). Cross-sectional scanning electron microscope inspections along with X-ray diffraction analyses revealed that it is possible to grow a 20 μm thick Fe₂B layer in 30 min at the condition of 1/4 duty cycle, 200 mA/cm² current density and 950 °C. Additionally, the average diffusion coefficient model calculations were done which gave a good correlation with experimental results.