Process-microstructural features for tailoring fatigue strength of wire arc additive manufactured functionally graded material of SS904L and Hastelloy C-276

[Display omitted] •WAAM process was successfully used to fabricate FGM of SS904L/Hastelloy C-276.•Heterogeneous microchemistry along the built-direction is attributed to the complex cyclic thermal history.•FGM tensile samples fractured with sufficient plastic deformation and tensile strength higher than SS904L wrought alloy.•FGM samples tested 105 cycles showed smooth surfaces. Many engineered components on subjecting to critical environments require properties that slightly differs with location in the fabricated part. The inadequate understanding of wire arc additive manufacturing (WAAM) process-microstructural features correlation brings interests on the structural reliability of functionally graded materials (FGM), which limits the extensive use of this cutting edge technology. Gas metal arc welding (GMAW) based WAAM process was adopted to fabricate the FGM of super austenitic stainless steel SS904L and Hastelloy C-276 with excellent bonding. The micrographs revealed that the WAAM processed FGM was mainly composed of columnar and equiaxed dendrites and had noticeable inhomogeneous features along the built direction. Tensile test results of sample along the built direction revealed a yield strength of 311.08 MPa and tensile strength of 680.73 MPa. Cyclic loading results depicted that the WAAM processed FGM has a fatigue resistance of 156 Mpa after sustaining 2 × 106 cycles. As a result of the varying microstructural characteristics along the built direction, the failure was initiated and fractured at the SS904L weaker region.