Kinetic Investigation and Wear Properties of Fe2B Layers on AISI 12L14 Steel

Analysis of the growth kinetics of Fe2B layers by the integral method

“…C 0 is the solubility limit of boron within the material substrate which can be neglected (0 wt.%) [29,30]. The following assumptions considered during the establishment of diffusion model can be found elsewhere [23][24][25].…”

“…This resulting DAE system can be solved either analytically [23][24][25] or numerically [32].To get the expression of boron diffusion coefficients in Fe 2 B, an analytic solution exists for this diffusion problem by setting: (11) and by choosing the expressions for a(t) and b(t) as :…”

“…After substitution of Equations (11), (12) and 13into Equation 7and derivation with respect to the time, Equation (19) was deduced [23][24][25]. This last equation allows us to calculate the value of boron diffusion coefficient in Fe 2 B at the considered boriding temperature.…”

“…In the current study, an alternative diffusion model [23][24][25] using the integral method was applied to determine the boron diffusivity in the Fe 2 B layers on the Armco iron substrate in the range of 1123 to 1273 K.…”

“…Therefore, the numerical solution by the integral method was obtained without assuming a priori a parabolic growth law for the Fe 2 B layer and considering the boride incubation time of 1758.1 s with the initial values of u(t 0 )=0.01 µm, a(t 0 )=16.8409 and b(t 0 )=15.9067. For the diffusion model [13], the simulated value of Fe 2 B layer thickness was estimated from Equation (23): (23) with and =0.0973 where is given in (m 2 s -1 ) for an upper boron concentration in the Fe 2 B phase equal to 9 wt.%. It is also noticed that the determined value of boron activation energy for Armco iron from the diffusion model [13] is very comparable to the result given by the integral method.…”