This study investigates the fabrication of a functionally graded material (FGM) combining Inconel 825 (IN825) and austenitic stainless steel (SS) 309LSi using the pulsed cold metal transfer (pulsed CMT) wire arc additive manufacturing (WAAM) process. The aim of this study is to evaluate the mechanical and microstructural properties of the produced FGMs.
Defect-free FGMs were fabricated without solidification cracking or porosity at the interface region (IF). Microstructural characterization, including elemental mapping, energy-dispersive spectroscopy and X-ray diffraction, was conducted to examine compositional gradients, grain structures and phase distributions. Tensile testing and hardness measurements were performed to assess the mechanical properties of the FGMs.
Microstructural analysis revealed a smooth compositional gradient across the IF and refined grain structures due to the controlled heat input of the Pulsed CMT process. The IN825 region exhibited secondary precipitates enriched with molybdenum (Mo) and titanium (Ti), contributing to strength through precipitation hardening, while the SS 309LSi region displayed an austenitic-ferritic structure. The IF achieved an ultimate tensile strength (UTS) of 654 MPa, surpassing similar dissimilar material systems. Failure during tensile tests occurred in the SS 309LSi region due to its lower strength and the fracture surfaces exhibited ductile characteristics. Hardness measurements confirmed a gradual increase from SS 309LSi to IN825, reflecting the graded properties.
This study demonstrates the potential of pulsed CMT-based WAAM to produce FGMs with excellent mechanical and microstructural properties. The findings provide a cost-effective pathway for creating high-performance material combinations for advanced engineering applications.
