Comparative study of inertia and continuous drive friction welding processes based on equivalent energy input

Rotary friction welding can be performed using either continuous drive friction welding (CDFW) or inertia friction welding (IFW), which utilizes stored energy in a flywheel. Historically, these methods have distinct applications and geographic preferences: IFW is prevalent in the US, especially for superalloys, while CDFW is more common in Europe, focusing on automotive materials like steel and aluminum. This study presents a comparative analysis of both welding techniques using the same friction welding machine to minimize external variables. The free-machining steel AISI 1215, chosen for its banded microstructure, serves as the specimen material. The comparison is based on the same energetic input of 82.8 kJ to ensure consistency. However, IFW experienced significant losses due to internal friction, which further decelerated the spindle and reduced the effective weld energy to 68 kJ. Key findings include differences in deformation behavior and weld formation efficiency. CDFW exhibits a softer deformation, with principal shortening occurring during the forge phase due to axial force, resulting in large equiaxed inclusions in the weld zone. Additionally, less upset is generated with the same calculated energy input. In contrast, IFW demonstrates sharper deformation, with main shortening in the friction phase, achieving greater total upset. The combination of axial force and torque produces a spiralized material flow and finely dispersed inclusions due to high shear forces. These insights highlight the distinct advantages and characteristics of each welding technique, providing valuable information for their respective applications.