High-Temperature Fatigue Behavior of Inertia Friction Welded Joints of GH4065A Ni-Based Superalloy

Abstract

In this work, the novel Ni-based superalloy GH4065A inertia friction welding (IFW) joints were subjected to the post-welding heat treatments (PWHT) at 730 ℃ for 5 h or 760 ℃ for 5 h, and the differences in microstructure characteristics, local mechanical properties, and fatigue failure life were focused. Furthermore, based on the high-temperature low-cycle fatigue testing and characterization results, the correlation between the microstructure characteristics and low-cycle fatigue damage behavior was systematically analyzed. It was found that there were smaller grains in the thermo-mechanically affected zone (TMAZ) than in the weld zone and heat-affected zone (HAZ), and the boundary region between TMAZ and HAZ was the fatigue failure position of IFW joints under the high-temperature low-cycle fatigue loading. The fatigue testing results showed that the high-temperature fatigue performance for GH4065A IFW joints degenerated with the increase in PWHT temperature. There existed cyclic softening and inhomogeneous fatigue damage in an IFW joint, which was more significant under the 760 ℃ 5 h PWHT condition. Microstructurally, dislocation tangles and cells formed in the boundary region between TMAZ and HAZ under the fatigue loading. The difference in grain size after the IFW process and the inhomogeneous γ′ phrase re-precipitation after the PWHT in the boundary region between TMAZ and HAZ resulted in the local inhomogeneous strengthening, corresponding to uneven plastic deformation and fatigue failure behavior under the fatigue loadings.