Development of Phase-Field Model of Boronizing Process on Steels

Abstract Boronizing is a thermo-chemical treatment that has been widely used to improve surface characteristics of metal. However limited study can be found on the detail behavior of phase transformation during this process. Therefore the present research tries to develop phase-field model to simulate the boride phase growth on the iron steels. The phase-field equations were derived from Ginzburg-Landau free-energy functional using Allen-Cahn and Cahn-Hilliard equations. Pre-exponential factor for interface mobility, M0, and temperature of process, T, were used as the variable parameter. It was observed, even though the present variations of M0 does not influence the phase transformation rate, an optimization of this parameter is required in order to meet a good agreement between the phase transformation rate and boron concentration profile, since a slight difference of boron concentration profile was found for the variations of M0 parameter. On the other hand, it was also observed that as the temperature of process increases from 1000K up to 1300K there is an increasing of phase transformation rate, which is also confirmed by the higher diffusion of boron. These observations agree with the previous finding that higher temperature is required in order to create more Fe2B phase from austenite phase