Growth, characterization, and kinetic modeling of diiron boride layers on W302 steel

Abstract This study was focused on solid boriding of W302 steel, by using a Durborid powder with lowered active boron content, to obtain pure diiron boride layers. The processes were realized at temperatures from the range of 950–1050 °C and for holding times of up to 7 h. The obtained layer-to-substrate interfaces showed a very low degree of columnarity. X-ray diffraction analysis confirmed the presence of iron borides (Fe 2 B and traces of FeB). The growth of boride layers followed a parabolic relation with time. The thickness of boride coatings varied from 22 ± 1 to 82 ± 5.4 µm. The B activation energies were assessed through two models. The integral method and Taylor expansion model yielded the same activation energy (close to 206 kJ mol-1) with the difference in pre-exponent factors. The obtained results are useful for determining the optimum layer thickness for industrial applications where the wear is the most important issue. Graphical abstract