Hydroforming process of complex T-shaped tubular parts of nickel-based superalloy

Nickel-based superalloy thin-walled components have been used in aerospace equipments requiring high reliability and durability at high-temperature condition. To overcome the problem of severe thinning occurs in conventional one-step hydroforming, this paper proposes an innovative multi-step hydroforming process for manufacturing complex T-shaped tubular parts of nickel-based superalloy. The appropriate process parameters in every step for preventing undesirable wrinkling and splitting defects, including internal pressure, axial feeding length, axial feeding ratio, and retreating displacement of middle punch, have been determined through a detailed numerical simulation investigation. The results show that manufacturing of a GH4169 T-shaped tubular part with expanded diameter can be successfully implemented using a four-step hydroforming. Moreover, the four-step hydroforming process, as well as the forming defects and the thickness distribution of several typical sections on the hydroformed GH4169 T-shaped tubular part, are all discussed. Finally, the complex GH4169 T-shaped tubular part with a thickness more than 3 mm can be obtained successfully after the top of the side branch is removed. These results provide insights for the manufacturing of T-shaped tubular part with expanded diameter, and contribute to the development of superalloy tube forming process at room temperature.