Investigation of the interface between SLM processed nickel alloy on a cast iron substrate

Abstract

Recent advances in the field of additive manufacturing offers significant flexibility in shaping and processing of materials. These techniques have been extensively studied for the manufacturing of entire component, typically using powder of a single composition. In this study, we explore the use of selective laser melting technique for the processing of an existing component. The Inconel 625 powder was printed onto the cast iron coupons using selective laser melting. These processed coupons were then characterised to study the interface between the Inconel 625 layer and the cast iron substrate. The microstructure near the interface region transitioned from small equiaxed grains to columnar morphology. The chemical intermixing between the Inconel 625 and cast iron was mostly confined within the first layer of Inconel 625. No new phases were observed at or near the interface which is consistent with the predictions from the thermodynamic calculations that was carried out using the FactSage® software and typical process parameters and composition data. The microhardness measurements at and near the interface region showed the highest hardness values at the interface which can be related to the fine-grained microstructure and solid-solution strengthening of the region.