Diffusion Model for Simulating the Kinetics of Boronizing Process in the Case of FeB/Fe2B Bilayer Configuration

Abstract

In this work, we developed a diffusion model based on the second Fick's law and the solving of the mass balance equations of the (FeB/Fe2B) interface to simulate the boronizing kinetics in the case of bilayer configuration (FeB/Fe2B) formed on AISI D2 steel. It is known that the boronizing process is a thermochemical surface treatment generally carried out at temperatures ranging between 1223 K and 1323 K. The knowledge of the temperature and the processing time are necessary to simulate and optimize the boronizing process. The developed model in this study is used to estimate the value of the growth rate constant in each phase, to simulate the boride layer thickness formed on AISI D2 steel, to determine the boron concentration profile and to evaluate the mass gain at the surface of the borided AISI D2 steel. To validate the developed model, we used the experimental data taken from the literature concerning the layers thicknesses of FeB and Fe2B layers obtained for different process parameters. Finally, these experimental values are compared to the calculated results. A good agreement was observed between the simulated results and the experimental data.

Simulating the Growth of Dual-Phase Boride Layer on AISI M2 Steel by Two Kinetic Approaches

“…In Table 2 are displayed the new kinetics constants at the (Fe 2 B/FeB) interface fitted with Equation (3). In Table 3 are grouped the calculated values of boron diffusivities in FeB and Fe 2 B and those of the non-dimensional parameters (ε 1 and ε 2 ) with the help of the integral method (see Equations (34) and (35)) between 1173 and 1323 K and for C FeB up = 16.40 wt.%. It is noticed that the numerical values of ε 1 and ε 2 are nearly constant.…”

“…Kinetically, different kinetic approaches have been established to control the growth kinetics of compact layers composed of Fe 2 B [15][16][17][18][19][20][21][22] or (FeB and Fe 2 B) [23][24][25][26][27][28][29][30][31][32][33][34][35] and formed on ferrous alloys. All these mathematical models help to select the optimum values of boride layers' thicknesses according to the requirements imposed by the utilization of these ferrous materials in the industry.…”

“…Delai et al [29] have used the classical diffusion models to follow the boriding kinetics of 4Cr5MoSiV1 steel grade between 860 and 980 • C by getting a bilayer configuration (FeB/Fe 2 B) and neglecting the existence of incubation period during its formation. The same kinetic approach was also used by Belguendouz et al [34] to investigate the growth of FeB and Fe 2 B layers on AISI D2 steel by considering the boron diffusivity in the iron phase and by ignoring the influence of boride incubation periods on the kinetics.…”