Abstract
Two kinetic approaches (integral method and Dybkov method) have been applied for simulating the boriding kinetics of AISI M2 steel in the range of 1173 to 1323 K, by including the effect of incubation periods. For the integral method, a peculiar solution of the resulting system of differential algebraic equations (DAE) has been employed for assessing the diffusivities of boron in FeB and Fe2B. The boron activation energies in FeB and Fe2B have been deduced from both approaches and compared with the data taken from the literature. Furthermore, to experimentally extend the validity of both approaches, four additional boriding conditions obtained on the boronized samples at 1173, 1223, 1273 and 1323 K for 10 h were then used. The predicted boride layers’ thicknesses were confronted to the experimental values. Consequently, a satisfactory concordance was obtained when comparing the simulated layers’ thicknesses to the experimental values derived from the literature.
Highlights
Boriding treatment is a method of enrichment of the surface of steels or Armco iron by a thermal diffusion of atomic boron from boron-containing media [1] between 800 and 1050 ◦C for 0.5 to 10 h
In order to validate their diffusion model related to the continuity equations, the samples were borided at each temperature for a time duration of 10 h
Two kinetics models have been proposed to predict the kinetics of boronizing of AISI M2 steel when forming a bilayer (FeB + Fe2B)
Summary
Boriding treatment is a method of enrichment of the surface of steels or Armco iron by a thermal diffusion of atomic boron from boron-containing media [1] between 800 and 1050 ◦C for 0.5 to 10 h. The same kinetic approach was used by Belguendouz et al [34] to investigate the growth of FeB and Fe2B 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. The integral method [25,26] with a new variable changes and the Dybkov model [25,28] were suggested for simulating the boronizing kinetics of AISI M2 steel in the range of 1173 to 1323 K by using the experimental results [23] These two kinetic approaches have been checked empirically by confronting the experimental layers’ thicknesses to the simulated values. The mass gain in each iron boride layer was evaluated in dependence of exposure time that is greater than the boride incubation period
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