EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Inconel625 is a nickel-based alloy characterized by high strength at high temperature and corrosion resistance in harmful environments. Unfortunately, high hardness, poor machinability and low thermal conductivity make it difficult to fabricate components with a complex shape. These problems can be solved using additive manufacturing (AM). Application of AM Inconel625 in an aggressive environment requires investigation of the influence of the manufacturing technology on the microstructure and corrosion resistance.
The aim of this work was microstructural investigation of Inconel625 additively manufactured using laser-assisted powder bed fusion (L-PBF) and direct energy deposition (L-DED) technology and characterization of its resistance to electrochemical corrosion in H2SO4 solution. The microstructure was investigated by means of LM and SEM combined with microanalysis of chemical composition by EDS. The corrosion resistance measurements were performed using impedance spectroscopy and polarization curves techniques.
The LM observations of the L-DED and L-PBF Inconel625 in the plane parallel to the build direction revealed a fish-scale-like morphology of melt pools. The width of melt pool was in the range from 600 to 1400 µm for L-DED manufactured samples, while for L-PBF it was much smaller and ranged between 70 and 300 µm. SEM observations of both variants shown cellular-dendritic microstructure of the melt pools as well as precipitates of carbides and intermetallic phases in rich in Nb and Mo in the intercellular regions.
Electrochemical corrosion tests in H2SO4 solution showed the formation of protective layer of corrosion products. The change of the corrosion current after 1 and 7 days of H2SO4 exposure was similar for both variants and ranged from 1.7910^-8 to 1.4410^-9 A/cm2 for L-DED and from 1.4610^-8 to 4.6110^-9 A/cm2 for L-PBF.
Acknowledgments: The study was
supported by AGH-UST (project no. 16.16.110.663).