A review on the multi-scaled structures and mechanical/thermal properties of tool steels fabricated by laser powder bed fusion additive manufacturing

The laser powder bed fusion (LPBF) process can integrally form geometrically complex and high-performance metallic parts that have attracted much interest, especially in the molds industry. The appearance of the LPBF makes it possible to design and produce complex conformal cooling channel systems in molds. Thus, LPBF-processed tool steels have attracted more and more attention. The complex thermal history in the LPBF process makes the microstructural characteristics and properties different from those of conventional manufactured tool steels. This paper provides an overview of LPBF-processed tool steels by describing the physical phenomena, the microstructural characteristics, and the mechanical/thermal properties, including tensile properties, wear resistance, and thermal properties. The microstructural characteristics are presented through a multiscale perspective, ranging from densification, meso-structure, microstructure, substructure in grains, to nanoprecipitates. Finally, a summary of tool steels and their challenges and outlooks are introduced.