SIMULATION OF GROWTH KINETICS OF Fe2B LAYERS FORMED ON GRAY CAST IRON DURING THE POWDER-PACK BORIDING

摘要

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 bonding. The kinetic-diffusion model considers the mass balance equation of the (Fe2B/Fe) interface with the purpose of determining the boron diffusion coefficients (D-Fe2B) in the Fe2B layers. The kinetic model 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 bonding. 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 5 h of treatment time. The X-ray diffraction method (XRD), the energy dispersive spectroscopy (EDS) and the adherence of the layer/substrate were applied.