Diffusion behavior and mechanical properties of high chromium cast iron/low carbon steel bimetal

In the present study, a high chromium cast iron (HCCI) as the high hard and wear-resistant layer was bonded on the surface of low carbon steel (LCS) at 1633 K. The microstructure and mechanical properties of the bimetal were investigated. The results show that the HCCI and the LCS were bonded well, the shear strength value is 539.6 MPa. No defect such as unbonded regions, microvoids and microcracks on the interface was observed. C atoms diffuse from the region of low concentration (LCS) to the region of high concentration (HCCI) across the interface during the diffusion process, which belongs to the uphill diffusion phenomenon. The thickness of the diffusion zone is about 55 µm. The troostite consisting of M₂₃C₆ and ferrite showed up instead of M₇C₃ in the diffusion zone. The spacing of M₂₃C₆ lamellar is 63 nm in average, and the Fe/Cr atom ratio of M₂₃C₆ is approximately 2.4. A certain number of grains formed across the interface, which improved the interface bonding strength effectively. The tensile strength of the bimetal is 447.9 MPa, cleavage fracture appeared in the HCCI side. The bending strength (1208.4 MPa) and impact strength (75 kJ m⁻²) both enhanced obviously compared with the HCCI.