abstract
- In the present study, an alternative diffusion model was proposed for analyzing the growth of Fe2B layers formed on the AISI 4140 steel during the pack-boriding process. This model was based on solving the mass-balance equations for the Fe2B/Fe interface to evaluate boron diffusion coefficients through the Fe2B layers in a temperature range of 1123-1273 K. The boride incubation time for the Fe2B phase was included in the present model. The suggested model was validated experimentally at a temperature of 1253 K for a treatment time of 5 h. Furthermore, the generated boride layers were analyzed with light microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction analysis (XRD). In addition, a contour diagram was also proposed as a function of treatment time and temperature. On the basis of our experimental results, the boron activation energy for the AISI 4140 steel was found to be 189.24 kJ mol-1.