Technology for solid-state pack boronizing of Q235 steel and kinetic study of boron diffusion in steel

Q235 steel was pack boronized with solid-state agent. An attempt was made to investigate the possibility of predicting the thickness variation of boride layers. The experimental data were fitted with Sigma Plot 10.0 software. The iso-thickness diagram of the bonding layer was obtained, making it feasible to predict the thickness of the bonding layer by giving bonding temperature and time, and to determine suitable bonding temperature and time according to the target thickness of the bonding layer. Moreover, the diffusion factors such as diffusion activation energy and diffusion rate constant of the Q235 steel were analyzed with kinetics method according to the thickness of the boronized layers under different temperatures. Results indicate that bonding layer formed on the Q235 steel surface has saw-tooth morphology and is composed of single phase Fe2B. The diffusion rate constant (K) of boron atoms in the Q235 steel at 800 deg C, 850 deg C, and 900 deg C were calculated to be 1.074 x 10(-13), 1.622 x 10(-13)