Selective laser melting of Inconel 625 alloy with reduced defect formation

Abstract

Selective laser melting (SLM) of nickel-based superalloys, such as Inconel 625 (IN625), creates new opportunities for the additive manufacture of highly optimized engineered structures with high service temperature and exceptional resistance to oxidation and corrosion. However, SLM processing of IN625 can be challenging due to the occurrence of material defects such as porosity and microcracking. An experimental and analytical investigation has identified potential strategies for reducing the formation of defects through careful selection of processing conditions and modification of material composition, respectively. Reducing the inertial effects of the laser galvanometer with a laser skywriting function has been found to significantly reduce the formation of porosity defects. However, microcrack formation was not mitigated with the variation of the laser processing parameters. Thermodynamic simulations were used to predict the solidification behavior for several modified IN625 compositions, where silicon and manganese contents were varied within the standard material composition range. An index to predict the relative hot tearing sensitivity of each composition was calculated from the solidification data, which revealed that hot tearing susceptibility may be reduced by minimizing silicon and manganese. Application of the identified process and composition improvements can lead to SLM manufacture of defect-free IN625 components for high-value applications.