On the Abnormal Structure in Boronized Carbon Steel

In order to make clear the mechanism of the abnormal structure formation that was obtained sometimes between the boride layer and the matrix of boronized medium carbon alloy steel, carbon steels (S25C, S45C, SK5) were boronized and diffusion-annealed at various temperatures for various periods of time, and were investigated by X-ray diffractometry, high temperature microscopy and emission spectroscopy. The abnormal structure formation was found in all of the specimens treated at the temperatures of austenite field.It was considered that the formation of the abnormal structure was attributed to the austenite grain growth and the precipitation of borocementite caused by boron diffused to the inner part of specimen.