Search

MAX phases are promising candidate structural materials for lead-cooled fast reactors (LFRs) and accelerator-driven sub-critical systems (ADSs) due to their excellent corrosion resistance in liquid LBE. In this work, one of the typical MAX phases, Ti3SiC2, was exposed to the flowing LBE with a saturated oxygen concentration at 500 °C for up to 3000 h. The corrosion behaviors, including the evolution of the corrosion layer, mechanical properties and wettability, were evaluated via X-ray diffraction, a scanning electron microscope equipped with an energy-dispersive X-ray, a microhardness test and contact angle measurement. The results reveal that a corrosion structure with a duplex layer was formed on the sample surfaces. The outer layer was a diffusion layer, which always remained thin (<3 μm) during the whole test due to the erosion effect caused by the flowing LBE. The inner layer was the stable protective oxide layer, and its thickness increased with exposure time. The growth of the corrosion structure improved the microhardness and reduced the wettability with regard to LBE, which was beneficial to inhibiting further surface corrosion of Ti3SiC2. [ABSTRACT FROM AUTHOR]

For lead‐cooled fast reactors and accelerator‐driven subcritical systems, the surface corrosion behavior of candidate structural materials in lead–bismuth eutectic (LBE) is a key issue, which determines whether the material is applicable. The candidate materials of two typical MAX phases, Ti3SiC2 and Ti3AlC2, were immersed in static LBE with saturated oxygen concentration at 500°C for up to 3000 h. The corrosion behaviors of Ti3SiC2 and Ti3AlC2 were analyzed by scanning electron microscope, energy‐dispersive X‐ray, X‐ray diffraction, and Raman spectra. The experimental results showed that elements interdiffusion between LBE and sample matrix occurred on both Ti3SiC2 and Ti3AlC2 surfaces, which led to the formation of the diffusion layer. The dominant component of the diffusion layer is PbTiO3, which makes the corroded surface fragile in a stress environment. Besides, there were differences in structures of corroded sample surfaces between Ti3SiC2 and Ti3AlC2. The corrosion layer of Ti3SiC2 consisted of two layers, while only one single layer formed on Ti3AlC2 surfaces. The stable oxide layer consisting of SiO2 and TiO2 can protect Ti3SiC2 samples from further LBE corrosion and maintain the integrity of the surfaces. For Ti3AlC2 samples, it is hard to form a continuous Al2O3 protective layer, thus no stable oxide layer was detected on the corroded surfaces. Compared with Ti3AlC2, Ti3SiC2 showed better corrosion resistance in LBE. [ABSTRACT FROM AUTHOR]

MAX phase ceramics attract increased attention for lead-cooled fast reactors due to their promising compatibility with lead-bismuth eutectic (LBE). This work systematically investigates the corrosion behaviors of five Ti 3 Al 1−x Si x C 2 MAXs with Al/Si complex A component in static LBE at 550 ºC up to 3000 h. Based on the lattice structure, mechanical properties, surface morphologies, and elemental composition during corrosion, a synergism of Al and Si during oxidation and diffusion is found, which contributes to a continuous and well-attached Al 2 O 3 layer with improved LBE corrosion resistance. Therefore, the multi-element design will bring a broad space for the applications of MAX ceramics. • Ti3Al1−xSixC2 presents an enhanced corrosion resistance in Pb-Bi eutectic. • The continuous Al2O3 layer is proven as the crucial anti-corrosion species. • Moderate amount of Si is beneficial for a thin and continuous Al2O3 layer. [ABSTRACT FROM AUTHOR]

Liquid metal corrosion has become a critical issue in lead-cooled fast reactor when the steel encounters lead–bismuth eutectic (LBE). Although various coatings applied in LBE have garnered interest from many researchers, there are few reports on the compatibility of chrome carbide or chromium nitride coatings in LBE. Thus, Cr carbide and Cr-nitride coatings with thicknesses of 80 μm were prepared on 316H stainless steel (SS) to investigate the corrosion behavior in contact with static liquid LBE at 550 °C for 25, 76, and 207 h. These coatings were synthesized via pack chromizing and subsequent gas nitriding. The results showed that a distinct LBE penetration layer appeared on the surface of the as-received 316H SS after exposure to LBE. Pack-chromized coating and pack-chromized + gas nitride coating did not undergo obvious consumption in LBE in the early stages. Cracks in the pack-chromized coating promoted the preferential diffusion of oxygen and Pb Bi. The Cr in the pack-chromized + gas nitride coating slightly diffused outward to combine with oxygen to form Cr-oxide scale on the coating surface. These coatings act as a barrier to LBE corrosion, making the surface of the coating impermeable to LBE. • Cr atoms absorbed by 316 H SS during the chromizing treatment dissolved within the Fe in the substrate and formed a solid solution of Cr in α-Fe. • The outermost layer of the pack-chromized sample consists of Cr 23 C 6 (about 5 μm), with α-Fe (substrate) underneath. • Cr 2 N and CrN generated during the gas nitriding treatment is diffusely distributed inside the α-Fe phase. • The larger grain size of Cr 23 C 6 in pack-chromized coating is more prone to defects as cracks and pores in the normal oxide layer. [ABSTRACT FROM AUTHOR]

Fe x Al/Al 2 O 3 (x ≈ 3, 2, 1, 0.5) coatings are prepared on steel to investigate their potential for application in lead-cooled fast reactors through mechanical tests and corrosion tests. The results show that the increase of Al content in the transition layer changes its structure (ordered transition from α - Fe to B2), which enhances the hardness, brittleness, and wear properties of the coating, but decreases the bonding of the coating to the substrate (tough-brittle transition). In addition, Fe x Al/Al 2 O 3 coatings have excellent resistance to lead-bismuth eutectic. The Al content in the transition layer has an almost negligible effect on the lead-bismuth eutectic corrosion properties but increases the segregation of the Al element in the substrate. The segregations are mainly hexagonal and cubic AlN, and their generation mechanisms are elucidated in detail. [ABSTRACT FROM AUTHOR]