Abstract
Nickel-based alloys are good candidate structural materials for ultra-high temperature gas-cooled reactors due to their excellent mechanical properties under high-temperature conditions. The operating environment in the compact high-temperature gas-cooled reactor proposes more stringent requirements with higher displacement and temperatures higher than 700 °C. The irradiation resistance of nickel-based alloy 617 is evaluated by 120 MeV neon ion irradiation. The neon ion fluence is set with reference to the number of helium atoms generated by the reaction of (n, α) in nickel-based alloy under actual service conditions. With the application of an energy gradient degrader, the irradiation damage area is more uniform with increasing depth. The neon ion irradiation causes no significant surface damage to alloy 617 while the evolution of defects such as inherent dislocation lines is affected, thus leading to the deterioration of mechanical properties. By using the small punch test to analyze the irradiation effects, it is found that the neon ion irradiation results in the tendency of irradiation softening and does not lead to changes in the basic fracture characteristics under different annealing conditions. After annealing at 700 and 800 °C for 2 h, the irradiation embrittlement trend is intensified, with the fracture characteristic values of irradiated samples showing a more obvious decreasing trend.
Highlights
Chen explored the effect of annealing temperature on irradiated defects of nickel-based alloy by an in-situ annealing experiment by Xe ions
A nickel-based alloy (Ni-17Mo-7Cr) was irradiated with Xe ions, and the hardness of the alloy was measured using a nano-indentation instrument by Huang et al The results showed that compared with the unirradiated sample, the hardness of the irradiated sample showed a significant increase with the increase in the irradiation damage dose [11,12]
To analyze the surface damage of alloy 617 caused by high-energy neon ion irradiation, the surface morphology is observed with scanning electron microscopy (SEM)
Summary
Nuclear energy is low-carbon and clean, and the ongoing research of fourth-generation nuclear power technology is expected to ensure safe and efficient use [1]. Nickel-based alloys have excellent mechanical properties at high temperatures and can be used as candidate materials for the fourthgeneration reactor system. With the rise of irradiation temperature and dose, the size of irradiation-induced defects increased, while its density showed an opposite trend and decreased [7,8]. Chen explored the effect of annealing temperature on irradiated defects of nickel-based alloy by an in-situ annealing experiment by Xe ions. The results showed that the density of irradiation-induced defects did not change a lot when the annealing temperature is lower than 600 ◦C. After irradiating Hastelloy N alloy with Xe ions, the irradiation-induced defects tended to cluster near the inherent dislocations and modified the dislocations at a low damage dose. From 1956 to 1975, several nickel-based alloys (Alloy 600, 625, 706, 718, 800, Hastelloy X, A-286 and Rene 41) were irradiated under high temperatures in material test reactors. The small punch test (SPT) is used to analyze the irradiation effects on the tensile strength and fracture properties of alloy 617 before and after high temperature annealing
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