Interfacial characteristics and mechanical properties of X65/Inconel 625 composite plates at different rolling temperature

X65/Inconel 625 bimetallic composite plate can be used for deep-sea oil and gas transportation due to its low cost and excellent corrosion resistance. Hot rolling enables fabrication of high-performance bimetallic composite plates, but the optimal rolling temperature remains unclear. In this work, the effect of rolling temperature on interfacial microstructure and mechanical properties of X65/Inconel 625 bimetallic plates was systematically investigated. Four bimetallic plates were fabricated at different rolling temperatures from 950 °C to 1100 °C. An interlayer with a face-centered cubic (fcc) structure was consistently formed near the interface because of elemental diffusion, characterized by Fe < 85%, Ni > 8%, and Cr > 3.6%. The mechanical properties display a strong dependence on the rolling temperature. As the rolling temperature increases, the strength of Inconel 625 decreases and the interfacial back stress strengthening weakens, leading to a reduction in overall strength. The yield strength decreases from 532 ± 13 MPa to 411 ± 6 MPa, and the ultimate tensile strength decreases from 686 ± 16 MPa to 605 ± 6 MPa. In contrast, the elongation increases from 27.8 ± 2.8% to 37.8 ± 2.5%, and the interfacial bonding strength increases from 404 ± 2 MPa to 520 ± 9 MPa. The three-point bending performance meets the application requirements at all rolling temperatures. To achieve the highest tensile strength, 950 °C is recommended as the optimal finishing rolling temperature. The results can provide a theoretical basis for temperature control in hot rolling production of bimetallic composite plates.