Fatigue crack growth anisotropy, texture and residual stress in austenitic steel made by wire and arc additive manufacturing

Wire based additive manufacturing of metals is a novel and cost-effective method for the production of large-scale metallic parts in a wide range of engineering applications. While these methods display excellent tensile properties, relatively little is known of the microstructure-to-property relationships of wire-based additively manufactured stainless steel builds as they relate to fatigue and fracture behavior. Stainless steel alloy 304L walls were fabricated using wire and arc additive manufacturing and subjected to mechanical tests to characterize location and orientation dependant properties and microstructural features affecting crack growth. Fatigue crack growth rate analysis in the high cycle fatigue regime was undertaken on horizontally- and vertically-oriented single-edge notch bend specimens extracted at several positions from the wall. The R ratio was 0.1 and the test frequency was 10 Hz. Paris Law behavior similar to that observed wrought steel alloys has been achieved with vertical orientations showing the greatest crack growth resistance. In conjunction with mechanical testing, scanning electron microscopy and electron backscatter detection were used to assess microstructural effects on crack growth within the build.