Microstructural Features and Mechanical Integrity of Wire Arc Additive Manufactured SS321/Inconel 625 Functionally Gradient Material

The additively fabricated functionally gradient structures can be a potential replacement for conventionally manufactured structures via fusion welding techniques. A SS321/Inconel 625 functionally gradient material was processed by wire arc additive manufacturing (WAAM) process. The WAAM-formed SS321 comprises of equiaxed and columnar structures, while the Inconel 625 consists of dendritic structures. It can be concluded that a very narrow interface was formed between the additively manufactured SS321/Inconel 625 FGM without forming cracks or fissures. Energy-dispersive x-ray spectroscopy (EDS) element maps show a smooth transition of elements at the interface without much segregation while EDS point scan confirmed the presence of laves phase. The electron backscatter diffraction results at the interface region revealed continuous crystallographic growth with large elongated grains in the <001> orientation. Tensile properties were better for SS321 and comparable for Inconel 625 than the wrought alloys, while the interface FGM sample failed on the SS321 side. The micro-hardness steadily changed from 226-195 HV and 272-236 HV in SS321 and Inconel 625, respectively. The WAAM process demonstrates that successful FGM components can be fabricated with multi-material and controlled properties.