Microstructure and Mechanical Properties of 3D Printed Tool Steel after Various Precipitation Hardening Treatments

Precipitation hardening is one of the most frequently used methods of the post-processing heat treatments of 3D printed tool steel 1.2709, as it increases the yield and ultimate tensile strengths of the steel. Within this work, the broad temperature range of 250 degrees C - 550 degrees C was tested with five different holds at each temperature to study the effect of processing parameters on the microstructure and mechanical properties. Maraging tool steel 1.2709 was produced by selective laser melting (SLM) technology and obtained results were compared with conventionally produced steel of the same chemical composition. Mechanical properties were established by hardness measurement and tensile test and the microstructure was characterised mainly by light and scanning electron microscopy. The peak hardening was for both steels reached after 6 hours of precipitation at 500 degrees C, however, apparent hardening effects of heat treatment were observed already after low-temperature heat treatments.