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A b stra c t In the present work, a diffusion m odel was suggested to study the growth kinetics o f F e,B layers grown on the A ISI 1045 steel by the pack-boriding treatment. The generated boride layers were analyzed by optical microscopy and X-ray diffraction analysis. The applied diffusion m odel is based on the principle o f mass conservation at the (F e,B / substrate) interface. It was used to estimate the boron diffusion coefficients o f Fe,B in the temperature range o f 1123-1273 K. A validation o f the m odel was also made by comparing the experimental F e,B layer thickness obtained at 1253 K fo r 5 h o f treatment with the predicted value.Basing on our experimental results, the boron activation energy was estim ated as 180 kJ m ol'1 * fo r the A ISI 1045 steel.

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The AISI T1 steel was hardened by the solid boriding process in the temperature range 1123–1273 K for a time duration of 2 to 8 h. A kinetic model, based on the integral method, was applied to the growth of a single boride layer (Fe2B) at the surface of AISI T1 steel. This diffusion model has been validated experimentally by considering two additional boriding conditions. A numerical solution was then obtained after solving the set of differential algebraic equations in order to compare the experimental thicknesses of Fe2B layers with the predicted values. The activation energy for boron diffusion in AISI T1 steel was estimated as 212.76 kJ mol−1 and a comparison was made with other values available in the literature. The formed boride layers with a saw-tooth morphology were examined by scanning electron microscopy (SEM). X-ray diffraction confirmed that the borided layer was composed of only Fe2B. The Daimler-Benz Rockwell-C indentation technique was employed to assess the cohesion of Fe2B layers on AISI T1 steel. In addition, the pin-on-disc and wear scratch tests were carried out for investigating the wear behaviour of borided AISI T1 steel.

In the present work, the AISI S1 steel was pack-borided in the temperature range 1123-1273 K for 2-8 h to form a compact layer of Fe 2 B at the material surface. A recent kinetic approach, based on the integral method, was proposed to estimate the boron diffusion coefficients in the Fe 2 B layers formed on AISI S1 steel in the temperature range 1123-1273 K. In this model, the boron profile concentration in the Fe 2 B layer is described by a polynomial form based on the Goodman's method. As a main result, the value of activation energy for boron diffusion in AISI S1 steel was estimated as 199.15 kJmol-1 by the integral method and compared with the values available in the literature. Three extra boriding conditions were used to extend the validity of the kinetic model based on the integral method as well as other diffusion models. An experimental validation was made by comparing the values of Fe 2 B layers' thicknesses with those predicted by different diffusion models. Finally, an iso-thickness diagram was proposed for describing the evolution of Fe 2 B layer thickness as a function of boriding parameters.

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