Material mechanisms of nanometallic multilayer post‐weld treatment maximizing fatigue strength

Fatigue failure of metallic components is strongly influenced by surface properties, particularly in welded structures where stress concentrations at weld toes dominate crack initiation. Nanometallic multilayer (NMM) coatings offer a promising post‐weld surface treatment by simultaneously enhancing near‐surface microstructural and mechanical properties. This study investigated the material mechanisms by which saccharine addition modified residual stress state, microstructural evolution, and consequently the fatigue life of electrodeposited Cu/Ni NMMs as post‐weld treatment. Residual stress measurements showed that saccharine addition reversed the intrinsic tensile stress of additive‐free coatings (175±10 MPa) to compressive values exceeding ‐155±5 MPa. Introducing saccharine also suppressed cauliflower‐like surface morphology, thereby promoting grain refinement and highly uniform interfaces. Fatigue testing results demonstrated that both tensile‐ and compressive‐stressed NMMs improved fatigue performance relative to the as‐welded condition. However, the combined effects of compressive residual stress, refined surface morphology, reduced grain size, and interface‐mediated strengthening resulted in a significantly higher fatigue life for saccharine‐modified NMM coatings.

Content

DDC Class

620: Engineering