Growth Kinetics of the Fe2B Coating on AISI H13 Steel

A kinetic model was suggested to study the growth kinetics of Fe2B layers on AISI H13 steel via the pack-boriding method in the temperature range of 1123-1273 K. This model was based of the principle of mass conservation at the (Fe2B/substrate) interface where the boride incubation time was independent of the boriding temperature. The model was also validated experimentally by comparing the experimental Fe2B layers thicknesses with the predicted values at 1173 K during 7 h, 1223 K during 5 h, 1253 K during 2 h and 1273 K for 3 h. The Fe2B layers grown on AISI H13 steel were characterized by use of the following experimental techniques: optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analysis. In addition, a contour diagram describing the evolution of Fe2B layers as a function of the boriding parameters (time and temperature) was proposed. Finally, the boron activation energy for AISI H13 steel was estimated as 233 kJ mol-1 on the basis of our experimental results. This value of energy was compared with the literature data.