Interface microstructure and properties of vacuum billet forged 42CrMo/HSS composite roll

A vacuum billet forging process for the fabrication of composite roll is proposed by this paper and successfully manufactures 42CrMo/high-speed steel composite roll. The interface's morphology, structure, elemental distribution, and mechanical properties were characterized using SEM, EBSD, EPMA, TEM, tensile testing, and Oscilloscopic impact testing. The relationship between the interfacial microstructure and mechanical performance was systematically analyzed . Results demonstrated that heating at 1180 °C for 2 h, combined with a 40 % upsetting reduction and a single-pass elongation reduction below 10 %, achieves complete metallurgical bonding at the interface. Elemental diffusion of Fe, C, Cr, Mo, and V is evident, with Cr diffusion spanning approximately 46.5 μm. Tensile testing revealed strengths of 600 MPa, 695 MPa, and 665 MPa, and elongations of 12.6 %, 1.8 %, and 11.8 % for 42CrMo, HSS, and specimen containing the composite interface, respectively. Fractures in specimen containing the composite interface occurred about 3 mm from the interface on the 42CrMo side, highlighting the interface's excellent strength and ductility. Oscilloscopic impact tests indicated total impact energies of 34 J, 0.2 J, and 47 J for 42CrMo, HSS, and specimen containing the composite interface , respectively. The superior room-temperature impact toughness of the composite interface is attributed to coordinated deformation between the 42CrMo core and HSS layer. This coordination induces strain gradients at the interface during impact, enhancing strain hardening and improving crack initiation resistance, resulting in remarkable impact toughness.