Abstract
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 Fe2B at the material surface. A recent kinetic approach, based on the integral method, was proposed to estimate the boron diffusion coefficients in the Fe2B layers formed on AISI S1 steel in the temperature range 1123-1273 K. In this model, the boron profile concentration in the Fe2B 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 Fe2B layers’ thicknesses with those predicted by different diffusion models. Finally, an iso-thickness diagram was proposed for describing the evolution of Fe2B layer thickness as a function of boriding parameters.
Highlights
The boriding process is a thermochemical treatment in which the boron atoms are diffused into the surface of a workpiece to form hard layers composed of iron borides and metallic boride in the case of high alloy steels[1]
The AISI S1 steel was treated by the powder-pack boriding in the temperature range 1123-1273 K with a variable treatment time
The growth kinetics of Fe2B layers on AISI S1 steel was described by the classical parabolic growth law with the occurrence of a constant boride incubation time
Summary
The boriding process is a thermochemical treatment in which the boron atoms are diffused into the surface of a workpiece to form hard layers composed of iron borides and metallic boride in the case of high alloy steels[1]. Two kinds of iron borides can be formed by boriding in the temperature range 800-1050°C. The iron borides are interesting phases because of their high hardness. The powder-pack boriding is widely used in the industry because of its easy handling and low cost[2]. In this boriding method, a mixture of powders that consists of a boron yielding substance, an activator and a diluent is used. The samples to be borided are packed in a stainless steel container and placed in the furnace
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