Investigation of interfacial microstructure and mechanical properties of industrial-scale hot-rolled CS/SS composite plates for nuclear energy usage

Carbon steel (CS)-Stainless steel (SS) composite plates are becoming increasingly popular in the industry due to their combined advantage of corrosion resistance of SS and high strength of CS. The long-term service performance in the nuclear energy field requires high-quality interface bonding. This study systematically investigated the interfacial bonding properties and mechanisms of CS/SS composite plates industrially prepared via vacuum electron beam welding combined with hot rolling. Under multi-pass large hot rolling force conditions, the interface achieved excellent metallurgical bonding, and no obvious brittle intermetallic compounds were detected. Microstructures in the interfacial region were composed of fine dynamic recrystallization(DRX) grains and deformed structures. Significant diffusion of elements such as Cr, Ni, and Mo near the interface greatly facilitated interfacial bonding. High-resolution transmission electron microscopy analysis illustrated that the interface between ferrite and austenite was predominantly a semi-coherent interface with amorphous structure present in partial areas. The interfacial shear strength(ISS) reached 338 MPa, which was superior to the ISS of CS/SS composite plates prepared by traditional explosive bonding processes. This composite panel, with its excellent shear resistance and mechanical reliability, has been used in the auxiliary water tanks of the containment structures for China’s third-generation large-scale advanced pressurized water reactor nuclear power units. Its application in these projects has demonstrated its stability under severe operating conditions, providing practical evidence for material selection in the nuclear power industry and the global promotion of similar materials.