In low - carbon steel(0. 20% C), boronized layer is composed of FeB layer and Fe2B layer. In high - carbon steel (1. 0% C), boronned layer is composed of Fe2B layer. But in medium carbon steel (0. 45% C), it consists of several sub -layers, each of which is also composed of FeB layer and Fe2B layer. Pre - deformation reduce boronned layer depth in both low and medium steels (especially at 20% and 60% strain) and increases boronized layer depth in high carbon steel(especially at 40% strain).