The effective boron diffusion coefficient in Fe₂B layers with the presence of chemical stresses

In this study the effective boron diffusion coefficient (D _eff) was estimated in the Fe ₂B layer in the presence of chemical stresses. Boride layers were created at the surface of AISI 1018 borided steels by the paste boriding process, in which a 4-mm-thick layer of boron carbide paste was applied to the material surface. The treatment was carried out at 1123, 1173, 1223 and 1273 K with different exposure times for each temperature. The effective boron diffusion coefficients in the Fe ₂B layer were estimated by combining an expression that considers the stresses in the boride layer and the flux equation. In addition, an expression to evaluate the boride layer thickness was developed, and the calculated results were compared with the experimental data and the empirical models proposed in the literature.