| Abstract Scope |
Pipe components in olefin furnaces produced from cast heat-resistant Fe-Ni-Cr alloys have experienced premature failures during high temperature service by creep fracture, thermal fatigue, and/or thermal shock. These failure mechanisms are exacerbated by oxidation from furnace flue gases on their outer diameter (OD) surface and carburization from hydrocarbon-rich process fluids on their inner diameter surface (ID). To improve the service life of these components, a functionally graded material (FGM) based on a creep-resistant Fe-35Cr-45Ni (35/45) alloy with Si and Al additions has been proposed. Based on this concept, three filler metal compositions were selected/designed to fabricate an FGM by wire arc additive manufacturing (WAAM). The present study analyzes the cracking phenomena observed during WAAM of each individual filler metal, which are labeled 35/45, 35/45-Si, and 35/45-Al. WAAM builds from each filler metal were cross-sectioned and characterized by scanning electron microscopy (WAAM) to analyze cracking mechanisms. Across the builds, solidification, liquation, and reheat cracks were identified. Additionally, a unique ‘remelt’ cracking mechanism was identified that was associated with the complex evolution of Cr-rich carbides in areas of overlapping weld beads. The analysis in this work provided an understanding of the WAAM printability of each filler metal, which can inform further process parameter and filler metal composition development for the production of an FGM prototype. |