Effect of shot particle on the mechanism of creating a modified layer by atmospheric controlled IH-FPP treatment

Basic mechanisms of generating a surface modified layer formed by a previously developed atmospheric controlled IH-FPP system, consisting of induction heating system and fine particle peening system, were investigated. Three types of specimen treated at 900°C in argon with Cr, Al ₂O₃ and Cu shot particles were prepared. Surface microstructures of the treated commercialgrade pure iron were characterized with a scanning electron microscope (SEM), an energy dispersive X-ray spectrometer (EDX) and an X-ray diffraction analysis (XRD). When treatment was carried out using Cr particles, the transferred layer and the diffused layer of the shot-particle element formed at the treated surface. This was because the radius of Cr atom was almost the same as that of the Fe, thus forming a solid solution in the substrate. Conversely, when the treatment was applied using chemically stable Al₂O₃ particles, a transferred layer only was observed. In the case of Cu particles, adhesion occurred due to the low melting temperature of Cu particles, resulting in the formation of a thick adhesive layer such as that generated by thermal spraying. These results suggest that the characteristics of the modified layer, generated by the atmospheric controlled IH-FPP treatment system, can be controlled by varying the shot particles and other processing parameters.