Effect of Diffusion Annealing on Borides Layers Produced on XC38 Steel

In this work, we present a study of the effect of diffusion annealing at 700°C for 1 h on the nature and properties of boride layers obtained on XC38 steel through a molten salt consisting of borax (Na₂B₄O₇) and boron carbide (B₄C). We evaluated the changes brought by the diffusion annealing on the morphology of the boride layer, the thickness of this layer, the distribution of elements in the steel, and the hardness. Comparing the results obtained allowed concluding that the diffusion annealing will completely transform the two-phase layer formed of FeB and Fe₂B borides in a single-phase layer consisting of single boride Fe₂B. The transformation of the two-phase boride into a single-phase boride is done with an increase in thickness of about 30% compared to the initial thickness of the sample. The values of Si concentration obtained in the underlying zone after the diffusion annealing treatment are more important than those obtained in the same underlying zone of samples borided directly by immersion in molten salt consisting of borax and silicon carbide (SiC).