Metallurgical Characterization and Kinetics of Borided 34CrNiMo6 Steel

Abstract

Boriding of 34CrNiMo6 steel was performed in a solid medium consisting of Ekabor-II powders at 1123, 1173 and 1223 K for 2, 4 and 6 h. Morphological and kinetic examinations of the boride layers were carried out by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The thicknesses of the boride layers ranged from 22±2.3 to 145±4.1 depending on boriding temperature and time. The hardness of boride layer was about 1857 HV 0.1 after boriding for 6 h at 1223 K, while the hardness of the substrate was only around 238 HV 0.1 . Growth rate constants were found to be between 1.2×10 −13 – 9.8×10 −13 m 2 /s depending on temperature. The activation energy for boron diffusion was estimated as 239.4±8.6 kJ mol −1 . This value was comparable to the activation energies reported for medium carbon steels in the literature.