SIMULATION OF GROWTH KINETICS OF Fe2B LAYERSFORMED ON GRAY CAST IRON DURING THEPOWDER-PACK BORIDING

The modeling of the growth kinetics of boride layers is an important tool determining suitable process parameters for obtaining an adequate boride-layer thickness. In this study, a mathematical model of the growth kinetics of the Fe2B layers on gray cast iron was proposed for the powder-pack boriding. The kinetic-diffusion model considers the mass balance equation of the (Fe2B/Fe) interface with the purpose of determining the boron diffusion coefficients (DFe2B) in the Fe2B layers. The kineticmodel was set for the Fe2B layer thickness, assuming that the growth of boride layers follows a parabolic growth law. The presented model can be used to predict the Fe2B layer thickness formed on gray cast iron during the powder-pack boriding. This process was carried out in the temperature range of 1123?1273 K with the exposure times ranging from 2 h to 8 h. The reliability of the technique used is compared with the experimental value for the Fe2B layer thickness obtained at 1253 K after 5h of treatment time. The X-ray diffraction method (XRD), the energy dispersive spectroscopy (EDS) and the adherence of the layer/substrate were applied.