A Combination of Alloy Modification and Heat Treatment Strategies toward Enhancing the Properties of LPBF Processed Hot Working Tool Steels (HWTS)

Abstract

Hot working tool steels (HWTS) are popular for industrial applications such as injection molding tools, and casting dies because of their high wear resistance, fatigue, strength, and toughness properties, even at elevated temperatures. Conventionally, they go through multi-stage heat treatments in order to attain targeted microstructures. Achieving such microstructures with a laser powder bed fusion (LPBF) process will require tailor-made process parameters since it is characterized by non-equilibrium conditions, non-uniform temperature distribution, and metastable phase formation. Recent advances in the LPBF qualification of 1.2343/4 HWTS have shown commendable results but are still fraught with the limitations of poor ductility or extra post-heat treatment steps. For the industrial competitiveness of LPBF HWTS, the enhancement of strength and ductility and elimination of post processing is critical. Therefore, minimizing retained austenite in the as-built samples through pre-heat treatment or alloying to reduce post heat treatments without sacrificing strength will be economically important for industry. In this work, 1.2343 HWTS and its modified form were LPBF printed both in the as-built, pre- and post-heat-treated conditions. The results are discussed based on the correlations of the powder properties with LPBF—part density, microstructure, and mechanical properties.