Creep Behavior and Fracture Mechanisms of the Dissimilar Inertia Friction Welded Joints of Deformed and Powder Metallurgy Ni‐Based Superalloys

ABSTRACT In this research, the microstructure and precipitate characteristics of the dissimilar inertia friction welded (IFW) joints of deformed and powder metallurgy (PM) nickel‐based superalloys were studied using optical, scanning electron, and transmission electron microscopy. In addition, several creep tests were conducted. The high‐temperature mechanical properties of the IFW joints were systematically analyzed. Under the creep testing condition of 680°C, the specimens exhibited creep fracture at the thermomechanically affected zone (TMAZ) of the PM superalloys. Further, the failure lifetime is enhanced with a reduction in the applied creep loading. Owing to the IFW process, various γ′ precipitates and carbide distributions were observed in the various zones of a dissimilar IFW joint. Undissolved powder particle boundary (PPB) defects in the TMAZ of the PM superalloy initiated creep cracks under creep loading. Based on the experimental results and theoretical analysis, the creep fracture mechanisms of the dissimilar IFW joints were revealed. Thus, the findings of this study provide guidance for controlling the microstructures and properties of dissimilar deformed/PM nickel‐based superalloy IFW joints.