Microstructure Evolution in Additively Manufactured Steel Molds: A Review

Over the last decade, developments in metal additive manufacturing (AM) have opened up new possibilities in various industries. Current metal AM technologies are now capable of processing a larger selection of metals, including steel mold materials such as H13 and P20. In the injection molding industry, mold makers have implemented metal AM technologies to 3D print steel molds. The main challenge currently faced by mold makers is to 3D print steel molds with mechanical properties that are comparable with conventionally made ones. Research on the microstructure evolution in 3D printed steel molds provide the necessary information for tailoring the mold’s microstructure and improving its mechanical properties. This review presents a unique perspective on the microstructure evolution in 3D printed steel molds. The microstructure evolution is discussed according to two major processing stages. Stage 1 describes the formation of the mold’s microstructure in as-built condition after it has solidified from its molten state. Subsequently, Stage 2 describes the changes in the mold’s microstructure post-heat treatment. This review also summarizes the various experimental techniques and numerical models used to study the microstructure evolution in 3D printed components. Advances in experimental microstructure characterization techniques enable researchers to investigate microstructure evolution in situ during metal AM processes. Coupled thermal-microstructure numerical models serve as an alternative approach for predicting grain growth in 3D printed components. The review concludes by summarizing future prospects in mold making and metal AM research in general.