At the end of the boriding process when the temperature decreases to ambient, and if the duplex phase is produced in the boride layer, stresses from such phases can lead to crack formation at the FeB/Fe2B interface. This latter, due to those phases exhibit different coefficients of thermal expansion, it can cause spallation leading to the separation of the duplex layer, or else crack formation can appear under mechanical strain or ther- mal and mechanical shocks