Effect of Mo Content on Carbides at GBs and High-Temperature Tensile Properties of Inconel617 Alloy

Abstract:

Inconel617 alloy has significant application potential in Generation IV nuclear energy systems. The effects of Mo content on carbide precipitation at grain boundaries (GBs) and high-temperature tensile properties of Inconel617 alloy were studied by mechanical testing and advanced techniques such as scanning electron microscope, transmission electron microscope, and electron backscatter diffractometer. The results show that there are only fine granular M₂₃C₆ carbide at GBs when the Mo content ranges from 8wt% to 9wt%. However, as Mo content increases from 9.3wt% to 9.6wt%, massive M₂₃C₆ and M₆C carbides could be predominantly observed at GBs. As Mo content increases from 8.0wt% to 9.6wt%, the elongation increases initially and then decreases, and the alloys with the Mo content of 8.5wt%–9.3wt% achieve optimal strength-ductility balance. The fractographic analysis reveals that the precipitation of granular M₂₃C₆ at GBs effectively strengthens grain boundaries, resulting in the transgranular fracture features on the high-temperature tensile fracture surface. When massive M₂₃C₆ and M₆C carbides precipitate at GBs, the initiation of intergranular crack is promoted and the intergranular fracture features are observed on the high-temperature tensile fracture surface. The Mo content of Inconel617 alloy for high-temperature components in Generation IV nuclear systems cannot exceed 9.3wt% and it should be controlled with in the range of 8.5wt%-9wt%