Boronizing Kinetics of 30CrNiMo8 Steel

Boronizing is a thermochemical treatment performed to obtain hard surface layers that improve wear resistance. In this study, the boronizing kinetics of pack boronized 30CrNiMo8 steel is investigated. Boronizing was performed at 830, 880 and 930 °C for 4, 6 and 8 hours in DURBORID® G powder mixture. The boride layers obtained characteristic but less pronounced sawtooth morphology, which is typical for the boronizing of low-alloy steels. The average layer thicknesses were between 32,9 and 122 µm, depending on the boronizing temperature and duration, with the temperature having a greater influence. The kinetics of boride layer growth was investigated using the Arrhenius equation, and the results confirm that the boronizing process follows the parabolic law, i.e. that the kinetics of boride layer growth is governed by the diffusion of boron atoms. The activation energy is estimated to be 173,45 kJ/mol and the frequency factor to be 1,54 × 10–5 m²/s. Based on these results, a mathematical model was established to describe the relationship between the boride layer thickness, temperature and duration of boronizing of 30CrNiMo8 steel. This model is suitable for practical application as it allows a quick and easy estimation of the boride layer thickness based on the boronizing parameters.