This study aims to enhance the fabrication of functionally graded materials (FGMs) combining SS316L and Inconel 625 via selective laser melting (SLM) by addressing challenges such as interfacial porosity, surface roughness and corrosion susceptibility, to improve structural integrity and electrochemical performance for advanced applications.
SS316L/Inconel 625 FGM specimens were fabricated using an SLM platform with a gradual composition transition. In situ remelting and ultrasonic-assisted ball burnishing (UAB) were applied as optimization techniques. The effects on pore topology, surface integrity and corrosion behavior were evaluated using micro-CT, SEM, X-ray diffraction (XRD), surface roughness measurements, microhardness testing and electrochemical tests (Tafel and electrochemical impedance spectroscopy [EIS]).
Remelting significantly reduced porosity from 6.1% to 1.7% and improved interfacial bonding and phase uniformity, while UAB enhanced surface quality by reducing roughness from 6.3 µm to 1.5 µm. Corrosion analysis demonstrated that the remelted + UAB sample exhibited superior electrochemical behavior, with the lowest corrosion current density (0.12 µA/cm²), highest charge transfer resistance (85 kO·cm²) and a corrosion rate of only 0.012 mm/y.
This study pioneers a novel approach by integrating in situ remelting with UAB to enhance SS316L/Inconel 625 FGMs produced via SLM, overcoming key challenges in multi-material additive manufacturing. Departing from conventional methods that primarily address static properties, this work focuses on improving both surface integrity and electrochemical performance. This dual strategy establishes a robust framework for fabricating high-performance FGMs tailored for critical applications in aerospace, biomedical and marine sectors.
