Effect of the Boron Powder on Surface AISI W2 Steel: Experiments and Modelling

The effect of boron powder on surface AISI W2 steel and growth kinetic of the boride layer is studied. Boron powder mixture was used in the powder pack boriding; this process was carried out in the temperature range from 1173 to 1273 K with exposure times ranging from 2 to 8 h. The presence of boride was confirmed by optical microscopy, X-ray diffraction, and the distribution of alloy elements in boride layers with energy-dispersive spectrometry using scanning electron microscopy. A mathematical model of the growth kinetics of the single layer was proposed and boron diffusion coefficient was determined by mass balance equation. The morphology of Fe2B layer was smooth and boron activation energy in W2 steel was estimated as 187.696 kJ·mol−1. The kinetic model was validated with two experimental conditions, a contour diagram describing the evolution of Fe2B layer as a function of time and temperature parameters for industrial application.