Design against Fatigue of Super Duplex Stainless Steel Structures Fabricated by Wire Arc Additive Manufacturing Process

Additive manufacturing (AM) is increasingly used to make complex components for a wide spectrum of applications in engineering, medicine and dentistry. Wire arc additive manufacturing (WAAM), as one of AM processes, utilises electric arc and metal wire to fabricate fully dense and heavy metal parts at relatively low costs and high-energy efficiencies. WAAM was successfully applied in the production of several welding-based metal structures. Recently, there was a growing interest in WAAM processing of super duplex stainless steels (SDSS) due to their high strength and excellent corrosion resistance, which make them the prime choice for load-bearing structures in marine applications. Although a number of studies investigated the microstructural and mechanical properties of WAAM-processed SDSS components, little is known regarding their fatigue performance, which is critical in engineering design. This study reports on the outcomes of fatigue tests and fracture surface fractography of WAAM-processed SDSS. The results obtained indicate a significant anisotropy of fatigue properties and fatigue crack initiations resulting from internal defects rather than surface flaws. Based on these experimental results, we suggest an effective design methodology to improve the fatigue life of the WAAM-fabricated SDSS components. We also indicate that post-manufacturing surface treatments should not be underlined for the enhanced fatigue resistance of WAAM-processed SDSS structures