Wei Zhang

The influence of Au-ion irradiation on the microstructure and corrosion resistance of 12Cr ferritic/martensitic (F/M) steels in lead-bismuth eutectic (LBE) were systematically examined. The results indicated that numerous dislocation loops and high-density dislocation networks were found in the post-irradiation samples. Meanwhile, the irradiation-induced hardening and the amorphization of M23C6 were also observed. Following exposure to LBE, the structure of duplex-layer oxides in 12Cr F/M steels remained unchanged by irradiation, but the thickness increased obviously. This was caused by irradiation-induced defects which can provide additional diffusion pathways to accelerate the elements diffusion.

Ferritic/martensitic (F/M) steels are considered optimal candidates for utilization as structural materials in Lead-Cooled Fast Reactor (LFR) due to their excellent mechanical properties at high temperatures and outstanding resistance to irradiation swelling. However, the combined effect of lead-bismuth eutectic (LBE) corrosion and irradiation damage degrades the performance of structural materials and reduces their safe service life limits. Accordingly, this study investigated the LBE corrosion behavior of 9Cr F/M steels with different Si contents, which had been irradiated with 6 MeV Au ions. Furthermore, the influence of Si content on the irradiation damage and corrosion behavior of 9Cr F/M steel was discussed. With increasing irradiation dose, both the size and density of dislocation loops increased, leading to irradiation hardening. Irradiation-accelerated LBE corrosion was observed in samples with different Si contents, and the sample with 0.7 wt% Si content exhibited superior LBE corrosion resistance under irradiation-corrosion synergy.

The high-temperature lead-bismuth eutectic (LBE) corrosion resistance and ring compression performance of the Fe15Cr11Al2Si, Fe15Cr11Al0.5Y, and Fe15Cr11Al2Si0.5Y coatings were investigated. Even if the corrosion test temperature reaches 800 °C, all these coatings can effectively protect the steel cladding tube. After the corrosion test temperature exceeded 660 °C, an obvious Al-rich oxide layer was formed on the surface of the coating, and Al element enrichment occurred at the interface between the coating and the substrate. After the corrosion test at 800 °C, holes appeared in the thick interface layer of the Fe15Cr11Al2Si0.5Y coating. The Fe15Cr11Al2Si coating cracked after the ring compression test with a deformation rate of 3%, and the coating peeled off after the deformation rate reached 5%. When the deformation rate reached 5%, there was still no cracking in the Fe15Cr11Al0.5Y coating. When the deformation rate reached 30%, the coating cracked, but the cracked coating was still tightly bonded with the substrate. The Fe15Cr11Al2Si0.5Y coating has the worst compression performance, even if the deformation rate is 1%, the coating still peels off obviously. The underlying mechanism for the evolution of corrosion resistance and compression performance was discussed.

The bonding strength and LBE corrosion resistance of the Fe15Cr11Al2Si, Fe15Cr11Al0.5Y, and Fe15Cr11Al2Si0.5Y coatings heat‐treated at 500–650°C for 500 h were investigated. The results showed that the as‐deposited Fe15Cr11Al0.5Y coating has the strongest bonding strength with the F/M steel cladding tube compared with the Fe15Cr11Al2Si and Fe15Cr11Al2Si0.5Y coatings. Heat treatment deteriorates the bonding performance of the coatings, and obvious enrichment of Cr and Al elements appeared. The consumed Al element inside the heat‐treated coatings promotes the formation of Fe₃O₄ on the surface of the coatings after the corrosion test. The Y element can inhibit the enrichment of elements and the formation of Fe₃O₄. The bonding strength of the heat‐treated coatings can be improved after the corrosion test. The underlying mechanism of the evolution of microstructure and properties of the coatings after heat treatment and corrosion test was discussed.

Seven FeCrAlY-Al₂O₃ nanoceramic composite coatings are deposited on F/M steel via plasma spraying and laser remelting. A systematic investigation is conducted to examine the dependence of microstructure, mechanical properties, and lead–bismuth eutectic (LBE) corrosion resistance on the nano-Al₂O₃ addition and different Cr and Al contents. With the increase in Al content in FeCrAlY, gradual refinement of the coating grains occurs. The addition of nano-Al₂O₃ promotes the elemental segregation and precipitation of the second phase. The nano-Al₂O₃ notably enhances the mechanical properties of the coatings that are primarily attributed to second-phase and fine-grain strengthening. After LBE corrosion tests, intergranular corrosion morphology could be observed, where the contents of Cr and Al significantly influence the corrosion behavior of the coatings at varying temperatures.

FeCrAlY coatings deposited on the outer surface of the cladding tube by the magnetron sputtering with varying bias voltages (0 V to −500 V) were corroded at 550°C to 600°C in oxygen-saturated and oxygen-poor lead-bismuth eutectic for 500 h to 1,000 h. The increased bias voltage led to the Al content decreased and the Y content increased. The coating changed from columnar crystals to equiaxed crystals with increased bias voltage. The decreased bias voltage makes an improved corrosion resistance. The fundamental process governing the evolution of microstructure and corrosion resistance in the FeCrAlY coatings was discussed.

The effect of FeCrAl sublayer composition on the microstructure and lead-bismuth eutectic corrosion behavior of the FeCrAl/YSZ (Yttria-stabilized zirconia) composite coatings was systematically investigated by SEM and XRD. The results show that the FeCrAl sublayer as a diffusion barrier and a bonding layer is beneficial to improve the corrosion resistance of the coatings. After corrosion, a slow-growing, continuous, and protective Al-rich oxide is formed at the interface between the YSZ and FeCrAl sublayer, which effectively hinders the inward diffusion of oxygen atoms and the outward diffusion of iron atoms. Especially, the Fe-12Cr-7Al/YSZ coating exhibits the best corrosion resistance even after corrosion at 700 °C. The microscopic corrosion mechanism of FeCrAl/YSZ coatings is elucidated.