Abstract
According to the International Institute of Welding, welded joints exhibit reduced fatigue performance due to inherent geometric stress concentrations and metallurgical alterations induced by welding and cooling processes. To address these limitations, researchers at Hamburg University of Technology have developed an innovative post-weld treatment referred to as nanometallic multilayer (NMM) treatment.
This approach involves the electrodeposition of a nanolaminate coating onto the weld seam, fully covering the connection region. Upon solidification, the tuneable NMM coating induces compressive residual stresses in the near-surface region of the steel substrate, provides a hard, high-strength surface layer, and simultaneously ensures ductile behaviour through a high interface density. These combined mechanisms effectively delay crack initiation and early fatigue damage.
Experimental investigations demonstrate a substantial enhancement in fatigue strength of butt-welded double-V joints from FAT class 80 to FAT class 225, corresponding to a service life extension of more than one order of magnitude. Results from multiple independent studies confirm the robustness and reliability of the NMM technology and underscore its potential to fundamentally reshape fatigue-resistant structural design.
However, a systematic translation of the experimentally observed fatigue strength improvement into practical gains in service life and associated reductions in CO2 emission – particularly at the national scale – has been lacking to date. This study addresses this gap by providing quantitative assessment of the potential environmental benefits of NMM technology. The results indicate that, when applied to steel bridge construction in Germany, the adoption of NMM-treated welded joints could reduce CO2 emissions by up to nearly 100% highlighting the technology's transformative potential for sustainable infrastructure development.
