Rate of growth of boride layers on stainless steels

Abstract

In this study, the case properties and diffusion kinetics of AISI 310 and AISI 430 steels borided in Ekabor-II powder were investigated by conducting a series of experiments at temperatures of 1123, 1223 and 1323 K for 2, 4 and 6 h. The boride layer was characterised by optical microscopy, X-ray diffraction technique and micro-Vickers hardness tester. X-ray diffraction analysis of boride layers on the surface of the steels revealed the existence of FexBy, CrxBy and NixBy compounds. The thickness of boride layer increases by increasing boriding time and temperature for all steels. Depending on the chemical composition of substrates, the boride layer thickness on the surface of the AISI 310 and AISI 430 steels was found to be 50.48 and 91.62 μm, respectively. The hardness of the boride compounds formed on the surface of the AISI 310 and AISI 430 steels ranged from 1658 to 2284 HV0.1 and 1762 to 2165 HV0.1, respectively, whereas Vickers hardness values of the untreated steels AISI 310 and AISI 430 were 276 HV0.1 and 328 HV0.1, respectively. Depending on temperature and layer thickness, the activation energies of boron in 310 and 430 steel were found to be 165.45 and 134.95 kJ/mol, respectively.