Characterisation of additively manufactured Inconel 718 alloy by using electrolytic extraction
Sammanfattning: The formation of non-metallic inclusions (NMIs) are common in all steel grades and it is not possible as of today to be able to remove all of them. The inclusions are categorised into endogenous (oxides, nitrides, sulfides, carbides, and phosphides), and exogenous (entrapment of nonmetals: slag, mold). Their morphology, size, number, chemical composition, and location are important parameters which need to be classified and controlled as they have a big impact on the final properties of steel grades. In this study, only endogenous NMIs for the superalloy Inconel 718 were investigated. An electrolytic extraction (EE) was performed to see if this was a suitable method to be used for the study of the NMIs in powder particles, and in a metal sample produced from metal powder. The results were compared with NMIs found in conventional Inconel 718. The powder particles and the NMIs were investigated on a scanning electron microscope (SEM) for mentioned parameters. When the NMIs were classified, it was found that four inclusions (Al2O3,TiNb-N, NbTi-C, NbTiCrMo-C) were found in the metal sample produced by the powder and three (TiNb-N, NbTi-C, NbTiCr-C) in the conventional sample. Two inclusion types were the same for both alloy 718 metal samples, but all inclusions differed in number, size, morphology, and location. Furthermore, the EE method did not work for the powder particles themselves, it was concluded that the EE method was suitable for the metal sample made out of metal powder, but not the powder particles. The EE method needs to be further developed and adapted for metal powder analysis.
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