Comparison and Analysis of Diffusion Models for the Fe2B Layers Formed on the AISI 12L14 Steel by Using Powder-Pack Technique

Boriding is a thermochemical surface treatment, a diffusion process similar to carburizing and nitriding in that boron is diffused into a metal base. An indispensable tool to choose the suitable process parameters for obtaining boride layer of an adequate thickness is the modeling of the boriding kinetics. Moreover, the simulation of the growth kinetics of boride layers has gained great interest in the recent years. In this chapter, the AISI 12L14 steel was pack-borided in the temperature range of 1123 – 1273 K for treatment times between 2 and 8 h. A parabolic law for the kinetics of growth of Fe 2 B layers formed on the surface of AISI 12L14 steel was deducted. Two diffusion models were proposed for estimating the boron diffusion coefficients through the Fe 2 B layers. The measurements of the thickness (Fe 2 B), for different temperature of boriding, were used for calculations. As a result, the boron activation energy for the AISI 12L14 steel was estimated as 165.0 kJ/mol. In addi-tion, to extend the validity of the present models, two additional boriding conditions were done. The Fe 2 B layers grown on AISI 12L14 steel were characterized by use of the following experimental techniques: X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy.