Kinetic study and characterization of borided AISI 4140 steel

Abstract

In the present study, an alternative diffusion model was proposed for analyzing the growth of Fe 2 B layers formed on the AISI 4140 steel during the pack-boriding process. This model was based on solving the mass-balance equations for the Fe 2 B/Fe interface to evaluate boron diffusion coefficients through the Fe 2 B layers in a temperature range of 1123-1273 K. The boride incubation time for the Fe 2 B 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 . Keywords: boriding, incubation time, diffusion model, growth kinetics, activation energy, adherence V tej {tudiji je predlagan alternativni model difuzije za analiziranje rasti Fe 2 B-plasti, ki nastane na jeklu AISI 4140 pri boriranju v {katli. Ta model temelji na re{itvi ena~be ravnote`ja mas na stiku (Fe 2 B/Fe) pri oceni koeficienta difuzije bora skozi Fe 2 B-sloje v temperaturnem obmo~ju 1123-1273 K. Inkubacijski~as borida za Fe 2 B-fazo je bil vklju~en v predstavljeni model. Predlagani model je bil eksperimentalno ocenjen pri temperaturi 1253 K in~asu obdelave 5 h. Poleg tega so bili izdelani sloji analizirani na svetlobnem mikroskopu, z vrsti~nim elektronskim mikroskopom (SEM), energijsko disperzijsko rentgensko spektroskopijo (EDS) in z rentgensko difrakcijsko analizo (XRD). Dodatno je bil predlagan {e konturni diagram kot funkcija~asa obdelave in temperature. Na podlagi eksperimentalnih rezultatov je bilo ugotovljeno, da je aktivacijska energija bora pri jeklu AISI 4140 189,24 kJ mol -1 .

Comparative Study of Conventional and Microwave-Assisted Boriding of AISI 1040 and AISI 4140 Steels

“…They examined the diffusion kinetics of the boron. They determined the boron activation energy as 189.24 kJ•mol -1 in AISI 41240 steel [29]. Dominguez et al borided AISI 4140 steel at temperatures of 850, 900, 950 and 1000 °C for 2, 4, 6 and 8 h. In this study, they found the boron activation energy for the Fe 2 B phase as 173 kJ•mol -1 .…”

Mechanical characterization of pack-boronized AISI 4140 and AISI H13 steels

“…Figure 1(a) shows the microstructural images of AISI 4140 steel boronized at 900 °C for 4 hours. When the boronizing layers are examined, a structure with porous but having a columnar morphology is encountered as in the literature [27]. Since the outermost surface of the coating is damaged due to the polishing process, it seems to be porous.…”

Simulation of the Growth Kinetics of FeB and Fe2B Layers on AISI D2 Steel by the Integral Method

“…By applying the boundary condition on the surface, Eq. (13) was obtained: (13) Taking into account the boundary condition at the (FeB/Fe 2 B) interface, Equation ( 14) was deduced as follows: (14) By integrating the second Fick's law between 0 and u(t) for the FeB phase and from u(t) to v(t) for the Fe 2 B phase and applying the Leibniz rule (see Appendix for more details), the two ordinary differential Eqs. (15) and (16) were obtained :…”