Microstructure and corrosion behaviour of a modified Si-rich austenitic stainless steel obtained by directed energy deposition

Over the last years, additive manufacturing (AM) techniques have been attracting a growing interest in view of their flexibility and design freedom. When considering metallic materials, AM techniques as Laser Powder Bed Fusion and Directed Energy deposition (DED) furthermore allows to design new metallic alloys and metal matrix composites that would not be attainable by conventional processes. In this context, the present work aims to elaborate a new Si-rich austenitic stainless steel with enhanced usage properties by taking advantage of the total dissolution of silicon carbides (SiC) particles during directed energy deposition of mixed stainless steel 316L + 10 % SiC powders.
The microstructures and local hardness of thick deposits of the modified stainless steel are characterized using SEM observations, XRD, Vickers micro-hardness and nano-indentation. DTA analyses in reverse mode (as proposed in Maurizi Enrici et al, Adv. Eng. Mater., 2021) are also considered to elucidate the solidification sequence of the new alloys. The evolution of corrosion behaviour is examined through Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization techniques. The role of the alloying elements in the formation of oxide layers and the mechanisms contributing to the corrosion resistance are discussed.