Experimental investigation of fatigue crack growth in wire arc additively manufactured ER2209 duplex stainless steel

This study investigates the fatigue crack growth (FCG) behaviour of ER2209 duplex stainless steel produced using wire arc additive manufacturing (WAAM). The effects of minimum-to-maximum load ratio ( R = 0.1, 0.3, 0.5), loading direction ( θ = 0°, 30°, 45°, 60°, 90°) and surface condition (as-built or milled) of the WAAM specimens on the FCG performance have been studied by means of 11 compact tension (CT) tests. The design, manufacture and fatigue testing of the specimens are described, followed by a discussion of the test results, including the Paris' law material constants, fatigue crack growth rates (FCGR) and crack trajectories. The test results showed that the FCGR increased with increasing load ratios. The effect of loading direction (i.e. anisotropy) on the measured FCG behaviour was found to be minimal. The FCG behaviour of the studied WAAM ER2209 duplex stainless steel was shown to be superior to that of conventionally-produced duplex stainless steel, while similar FCG behaviour was observed for the milled and as-built specimens. The observed FCGR behaviour was shown to be conservatively predicted by the provisions in two current standards — BS 7910 and IIW-1823-07. Macroscopic and microscopic fractographic analysis of typical CT specimens was undertaken, revealing transgranular fracture as characterised by numerous fatigue striations, secondary cracks and dimples. • Fatigue crack growth behaviour of WAAM ER2209 duplex stainless steel by compact tension tests. • Effects of load direction, load ratio and surface condition on the crack length development and FCG rate. • WAAM ER2209 steel having more superior FCG behaviour than traditional duplex stainless steel and international standards. • Fractographic analysis revealing transgranular fracture.