Preparation of Fe2B boride coating on low-carbon steel surfaces and its evaluation of hardness and corrosion resistance

Fe2B coating was prepared on low-carbon steel by surface alloying. A series of experiments were carried out to examine some surface properties of boride coating. The surface heat treatment of coated low-carbon steel was performed at 700°C, 800°C and 900°C for 2h, 4h, 6h and 8h under hydrogen atmosphere. The boride coating was revealed by XRD analysis and the microstructure of the boride coating was analyzed by scanning electron microscopy (SEM). Depending on the temperature and time of the process, the hardness of the borided low-carbon steel ranged from 99 to 1100HV. The hardness showed a maximum (about 1100HV) at 900°C for 8h. The corrosion resistance of the borided samples was evaluated by the Tafel polarization and electrochemical impedance spectroscopy (EIS). Shift in the corrosion potential (Ecorr) towards the noble direction was observed, together with decrease in the corrosion current density (Icorr), increase in the charge transfer resistance (Rct) and decrease in the capacitance (Cc), which indicated an improvement in corrosion resistance with increasing temperature and time of the treatment. ► A compact morphology was observed by preparing Fe2B coating. ► XRD studies confirm that the boride coating was constituted of Fe2B phase. ► The hardness increased with increasing heat treatment time and temperature. ► The boride coating provides corrosion protection, and then defined barrier properties.