A Preliminary Study on the Quality of Joining AISI 316 and AISI 3415 Steel by the near Solidus Forming Process

In this study, the Near Solidus Forming (NSF) process, which falls under the umbrella of semi-solid processes, was utilized to coforge an AISI 316 tube and an AISI 3415 rod into an as-forged valve geometry. The billet used for the process was kept as large as possible to increase the contact surface area between the two materials. The process was carried out at 1360 °C in a single stroke, almost completely filling the geometry. No joining was observed in areas where low strains were expected, but in regions with medium to high strains, cross-diffusion of 2–7 μm was observed. The presence of small oxide particles was also observed in the joint due to the bimetallic billet shape.