Investigation of boriding kinetics of AISI D2 steel

Abstract

A diffusion model was suggested to analyse the growth kinetics of Fe₂B layers formed on AISI D2 steel by the pack-boriding process. It was used to estimate the boron diffusion coefficients of Fe₂B in the temperature range of 1123–1273 K by applying the mass balance equation at the (Fe₂B/substrate) interface. The proposed model was validated experimentally at 1253 K for a treatment time of 5 h by comparing the experimental Fe₂B layer thickness with the predicted value. Furthermore, the pack-borided AISI D2 steel was characterised by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analysis. A contour diagram describing the evolution of Fe₂B layer thickness as a function of the process variables was also proposed. In addition, the boron activation energy for AISI D2 steel was found to be equal to 201·50 kJ mol⁻¹, on the basis of our experimental results.

Keywords:

• Boriding
• Diffusion model
• Growth kinetics
• Activation energy

Acknowledgements

The work described in this paper was supported by a grant of PROMEP and CONACyT México. The authors wish to thank Ing. Martín Ortiz Granillo director de la Escuela Superior Campus Ciudad Sahagún-Universidad Autónoma del Estado de Hidalgo for their valuable collaboration for this study.