Recent progress on additive manufacturing of steel-based functionally graded materials

Functionally graded materials (FGMs) are capable of achieving specific performances or functions through the design of graded compositions, microstructures, and properties. They have found extensive applications in aerospace, biotechnology, nuclear energy, and various other industries. Steel-based FGMs, as a major part of FGMs, have been extensively studied in order to achieve excellent properties, such as great strength and plasticity, superior thermal stability, and remarkable resistance to oxidation and wear. In addition, additive manufacturing (AM) enables the rapid and cost-effective production of complex components and has become a crucial method for creating steel-based FGMs in modern times. This paper presents an analysis of the recent progress of research on steel-based FGMs according to material gradient types and steel types. Moreover, the issues and challenges associated with steel-based FGMs are also discussed. These include the selection of the process parameters applicable to different materials, adjustment of the material compatibility to reduce harmful phase formation, and difficulty of preparing ultra-high-strength steels with excellent plasticity. At the same time, future directions for research are suggested while considering current research findings and the obstacles encountered. This study offers essential instructions for the future production of steel-based FGMs using AM technologies.