Harnessing gradient design and nanoprecipitate engineering towards superior tribological and mechanical properties

Inherent process defects for microstructural inhomogeneity and strengthening phase dissolution have attracted extensive attentions during the inertial friction welding. Herein, a novel synergistic strengthening mechanism of gradient design and nanoprecipitate coupled engineering induced by Post-Weld Heat Treatment (PWHT) was proposed to improve the tribological and mechanical properties of GH4151 superalloy inertial friction welded joints. An axial gradient characteristic of strengthening phases was observed within the as-welded joints with zone-dependent dissolution and coarsening behavior. Solution aging induced multiscale redistribution of strengthening phases, while double aging preserved primary γ’ phase and facilitated homogeneous precipitation of nanoscale tertiary γ’ phase. Additionally, a deep V-shaped grain distribution was induced by spatially varying thermo-mechanical coupling effects. Solution aging promoted the static recrystallization and resulted in 21.1% grain coarsening driven by high temperature. Conversely, grain refinement of 18.3% during the double aging was achieved by synergistic mechanisms of subgrain formation induced by static recovery and grain boundary pinning by nanoscale γ′ precipitates, thereby constructing a hierarchical gradient structure. Double aging welded joint exhibited enhanced wear resistance and mechanical properties, attaining a wear rate of 7.18×10 -5 mm 3 /(N·m), a microhardness of 554 HV and a shear strength of 1241 MPa. Crystal plasticity finite element model further confirmed that gradient subgrain structures was beneficial to alleviate the stress concentration, thus improving the service reliability. The above findings provide critical insights for high performance manufacturing of aero-engine components.