Die steel design for additive manufacturing

Abstract

A novel printable die steel was computationally designed and experiemtnally validated for selective laser melting (SLM), utilizing the advantages of the rapid solidification processes. During gas atomization, nanoscale TiN particles are intended to be in situ precipitated at 1790 °C, nucleating δ-ferritic grains. Additionally, the chemical composition is adjusted to stabilize a complete δ-ferritic solidification via Scheil modeling to enhance the printability of the die steel. This work further introduces the concept of the matrix die steels aiming to dissolve solidification and primary carbides during solutionizing at a targeted temperature of 1100 °C. Thus, the C-content is reduced to 1.4 mol.-% (0.3 wt.-%) compared to the benchmark H13 die steel which contains 1.85 mol.-% (0.4 wt.-%). Even though a lower C-content is used, optimizing M₂C driving force during tempering enables the die steel to achieve a peak hardness of 536 HV . Lastly, a superior thermal conductivity of 40 W m^-1 K^-1 is predicted at 450 °C for the BCC matrix of the printable matrix die steel. The material design is based on thermo-chemical models interfaced with thermodynamic calculations as implemented in the Calculated Phase Diagram (CALPHAD) method.