Effect of Preheating on Microstructure Evolution and Creep Properties of IN718 Processed by Laser Powder Bed Fusion

In the laser powder bed fusion (L-PBF) method, Ar gas flows to remove fumes and quenches the specimen surface during solidification. This rapid cooling induces solidification segregation and solidification cracking. Preheating, which relieves rapid cooling and decreases residual stress would be important. In the powder bed fusion EBM, preheating is commonly used to prevent smoke and charging. However, in the L-PBF method, using preheating is not always common. This work aims to clarify the thermal behavior during the L-PBF process using preheated base plate temperatures (200°C and 600°C) for the IN718 superalloy using COMSOL simulation and experiment. The creep properties and microstructure of IN718 were found to be influenced by the preheating temperature. The specimen preheated at 600°C exhibited longer creep life and elongation than the specimen preheated at 200°C because of a lower amount of Nb segregation in the specimen preheated at 600°C during the L-PBF process.