Abstract
The characterization of iron boride layers formed at the surface of gray cast irons is evaluated in the present study. The thermochemical treatment applies the pack-powder boriding process in order to produce the Fe₂B phase at the surface of the material. The treatment was carried out at three different temperatures (1173, 1223 and 1273 K) and four exposure times (2, 4, 6, and 8 h). What is more, the boride layers were evaluated by the Vickers microindentation test, the X-Ray Diffraction method (XRD) and by the Energy Dispersive Spectroscopy method (EDS). Considering the growth fronts obtained at the surface of the gray cast irons, the boride incubation time and the mass balance equation at the interface Fe2B/substrate, the boron diffusion coefficient on the borided phase was determined in the range of the treatment temperatures. Also, the mass gain on the surface of the borided gray cast irons was calculated assuming that the thermodynamic equilibrium remained constant during the process.

Key words
borides, diffusion, growth kinetics, hard coatings, gray cast irons, boriding

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