Impact of in Situ Heat Treatment Effects during Laser‐Based Powder Bed Fusion of 1.3343 High‐Speed Steel with Preheating Temperatures up to 700 °C

For laser‐based powder bed fusion (PBF‐LB) of high carbon steels, preheated build platforms can reduce thermal stresses and crack formation inside the generated material. Furthermore, the heat distribution during PBF‐LB is affected by laser energy input and heat transfer into the surrounding area. Depending on the preheating temperature and the thermal conditions during PBF‐LB, thermal gradients and different thermal exposure times of the manufactured layers can lead to in situ heat treatment effects. As a result, gradients in microstructures and properties are observed in the manufactured material. The effects are investigated on AISI M2 high‐speed steel (1.3343). Specimens are manufactured at platform preheating temperatures between 200 and 700 °C. Base plate and surface temperatures in the building layer are monitored by thermocouples and pyrometry. Local variations in the material microstructure and properties are determined and the effects of temperature distribution on microstructure and hardness are discussed.