Effect of Boriding Treatment on the Corrosion Behavior of Steels

In this study, the corrosion behaviors of AISI 420 and AISI 5120 steels borided in Ekabor-II powder at a temperature of 950 °C for 5 h were investigated in a 4% M HCI acid solution. The properties of the boride layer were evaluated by optical microscopy, X-ray diffraction, the micro-Vickers hardness tester. X-ray diffraction analysis of the boride layers on the surface of the steels revealed the existence of FeB, Fe₂B and CrB compounds. The boride layer thickness on the surface of the AISI 420 and AISI 5120 steels was found to be 50.62 μm and 148.74 μm, respectively depending on the chemical composition of the substrates. The hardness of the boride compounds formed on the surface of the AISI 420 and AISI 5120 steels ranged from 1854 to 2147 HV_{0, 05} and 1498 to 1892 HV_{0, 05} respectively, whereas the Vickers hardness values of the untreated steels AISI 420 and AISI 5120 were 340 HV_{0, 05} and 224 HV_{0, 05}, respectively. The corrosion resistance of the borided steels was higher compared with that of the unborided steels. The borided steels increased the corrosion resistances of the steels 6–8-fold.