A Study of Microstructural Tensile and Fatigue Properties Coupled with Digital Image Correlation of Hybrid Manufactured Inconel 718 Parts by Extrusion and Powder Bed Fusion

Abstract

To overcome challenges associated with additive manufacturing (AM), a combination of AM and conventional manufacturing (CM) can be explored, enabling the production of hybrid structures. Nonetheless, realizing aerospace hybrid structures requires investigation into the process–structure–properties relationships of the AM and CM material and the interface zone between them. Herein, Inconel 718 is deposited onto extruded bars of the same material by powder bed fusion (PBF). The interface zone from the CM zone to the PBF zone is investigated using destructive and nondestructive testing. It is found that fractures during tensile tests occur in the CM zone. The PBF zone proves to be stronger than the CM zone (average yield strength of 1295 and 1167 MPa, respectively). A higher strength of PBF parts is related to the finer microstructure of δ‐phase precipitates and dendrite cell structure. The fatigue limit of the hybrid samples is high (Sa = 305 MPa, R = 0.1). Coupled fatigue and digital image correlation at the highest stress amplitude show distinctive plastic flow dominating the CM zone. In reverse, fracture of hybrid parts at lower stress amplitudes forms preferentially in the PBF zone because of process‐related defects (gas pores and lack of fusion).