Lead Bismuth Eutectic Corrosion Research Articles

Microstructure, mechanical and oxygen-deficient lead-bismuth eutectic corrosion properties of FeCrAlTiMo high-entropy alloy coatings for fuel claddings

The FeCrAlTiMo high-entropy alloy (HEA) coatings were deposited on the ferritic/martensitic (F/M) steel fuel cladding tubes by magnetron sputtering technology to improve their lead-bismuth eutectic (LBE) corrosion resistance. The effects of bias voltage on the microstructure, mechanical and LBE corrosion properties of the FeCrAlTiMo coatings were systematically investigated. The LBE corrosion test shows that the coatings with a bias voltage of −150 V exhibit the best oxidation resistance after exposed to the oxygen-deficient LBE at 600 °C for 500 h, and can be used as a protective candidate coating material for lead-cooled fast reactor (LFR) application. The high-temperature LBE corrosion mechanism of the FeCrAlTiMo coatings under deficient oxygen concentration was also discussed in detail.

Insight into the fretting corrosion behavior of 316L steel in liquid lead-bismuth eutectic at 500°C

Due to flow induced vibration caused by coolant circulation, fretting corrosion inevitably occurs between fuel cladding, heat exchanger tubes and their holders in Gen IV lead-bismuth eutectic (LBE) cooled nuclear reactors. In the current work, fretting corrosion behavior of 316 L steel in oxygen-saturated LBE at 500 °C has been investigated. It is shown that within the gross slip regime, the microstructure under fretting interface presents a stratified structure, composed of third body layer, oxide scales and plastic deformation layer. At the early stage of fretting corrosion, the dominant damage mechanism is fretting wear, showing that the thickness of third body layer is much larger than that of oxide scale. As fretting time increases, the dominant damage mechanism is gradually changed to LBE corrosion and fretting wear together, as the visible oxide scale is formed next to the third body layer. Moreover, the growth rate of oxide scales under fretting interface is accelerated by over an order of magnitude compared to that when 316 L steel exposed to LBE directly. In particular, after 60 h exposure, the thicknesses of oxide scale related to the worn and unworn regions are ∼4.5 μm and ∼0.2 μm, respectively. The occurrence of such phenomenon is thought to be ascribed to the severe plastic deformation under fretting contact interface, since the crystal defects served as perfectional nano-channels can promote the diffusivity of oxygen atoms. In addition, the acceleration diffusivities of oxygen atoms caused by the local high contact stress may also be responsible for this matter.

LBE corrosion behavior of helium pre-irradiated martensitic steel

In the design of the spallation target of CiADS, T91 steel was selected for the most critical component, the beam window. A Si-modified martensitic steel (SIMP) has been currently developed, which has better corrosion resistance and is planning to replace T91 as a material of beam window in the future. In order to assess the effect of irradiation damage on the microstructure evolution and corrosion behavior of the SIMP, the pre-irradiated samples with irradiation doses from 5 × 1015 to 3 × 1017 He/cm2 exposed in static lead-bismuth eutectic (LBE) with saturated oxygen at 350 °C for 4000 h were investigated. Results show that pre-irradiation neither change the double-layer structure of the oxide layer nor significantly affect the corrosion rate. This may be due to the slow diffusion of elements at low temperatures, and the low irradiation dose not reaching the threshold for triggering accelerated corrosion.

General corrosion behavior and mechanism of ferritic/martensitic steel with and without TaWVCr coating in static oxygen-saturated lead bismuth eutectic at 550 °C

Here in present work, the ferritic/martensitic (F/M) steel HT9 and refractory TaWVCr high entropy alloy coated HT9 were tested in a static oxygen-saturated lead bismuth eutectic (LBE) at 550 °C through corrosion tests and slow strain rate tension tests to investigate the corrosion behavior and mechanism. The fracture pattern of HT9 and TaWVCr/HT9 both show the ductile fracture. Comprehensive microstructural characterizations from atomic-scale examinations to micro-scale fracture analyses were performed to illustrate the underlying mechanisms of the liquid LBE corrosion. It was revealed that the corrosion of HT9 is related to the surface oxide scale cracking, which propagates into the matrix but terminated in the Cr2O3 enriched zone at the crack tip. On the contrary, the stress concentration caused by local degradation of the TaWVCr coating accelerates the oxidation and dissolution of the coating in LBE, leading to the formation of a duplex oxide layer underneath the coating, which allows cracks initiate in the magnetite layer and annihilate in the chromite layer. The micrometer-scale penetrative oxide layer was found within the matrix, due to the inward diffusion of O through the diffusion channels such as dislocation channels of the matrix and the dissolution channels of the coating and this can accelerate the oxidation corrosion of the matrix.

Enhancing LBE corrosion resistance through inhibition diffusion approach for AlTixCrFe HEA coating

High-entropy alloy (HEA), when used as coating materials for structural steel in lead–bismuth eutectic (LBE) nuclear reactor, faces severe dissolution corrosion due to the diffusion of their constituents along grain boundaries. In order to mitigate dissolution corrosion, a method to enhance the LBE corrosion resistance of HEA is proposed by utilizing a second phase to inhibit elemental diffusion at grain boundaries. Herein, we used the laser cladding technique to prepare a series of biphase AlTixCrFe HEA coating with a body-centered cubic primary phase and a TiAl second phase. During the LBE corrosion process, a single-layer oxide layer (OL) formed on the HEA coating surface, and meanwhile there existed an internal oxidation zone (IOZ) formed beneath the single-layer OL at AlTixCrFe HEA coating interface, which gradually converted into the single-layer OL as the corrosion time prolonged. After 2000 h of corrosion, AlTi0.75CrFe HEA coating exhibited the lowest OL thickness (8.1 μm) and oxidation rate (0.065 μm2/h) because Al, Ti, and Cr acted as protective elements, rapidly forming a protective OL on the surface. Meanwhile, the presence of TiAl second phase at the grain boundaries impeded the mobility of elements, which improved the dissolution corrosion resistance and diminished its destructive impact on the protective OL.

Lead-bismuth eutectic corrosion behavior of NbMoVCr refractory multi-principal element alloys coating synthesized by magnetron sputtering

Nanocrystalline NbMoVCr refractory multi-principal element alloys coatings are fabricated by magnetron sputtering technology to improve lead-bismuth eutectic (LBE) corrosion resistance of structural materials, and their corrosion behavior in oxygen-saturated liquid LBE at 600 and 650 °C has been investigated. The coatings exhibit good phase structural stability even at 650 °C exposure. Moreover, the coatings show promising LBE corrosion resistance with parabolic oxidation rate constant 3–5 orders of magnitude lower than other candidate steels (such as 316 L, HT9, T91, SIMP, CLAM, etc.) which is due to the formation of protective (CrV)2O3 solid solution layer. The oxidation process of the coating is mainly dominated by kinetic factors, including diffusion driving force (related to LBE solubility) and diffusion energy barrier (related to atomic radius). By the way, at the grain boundaries with much lower oxygen potential, thermodynamic factors dominate the oxidation process, and V with the highest oxygen activity shows evidence of selective oxidation.

Synergism of Al and Si occurs on corrosion of Ti3Al1−xSixC2 MAX in the static Pb-Bi eutectic at 550 ºC

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 Ti3Al1−xSixC2 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 Al2O3 layer with improved LBE corrosion resistance. Therefore, the multi-element design will bring a broad space for the applications of MAX ceramics.

Microstructure, Mechanical Properties, and Lead–Bismuth Eutectic Corrosion Behaviors of FeCrAlY-Al2O3 Nanoceramic Composite Coatings

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.

Preparation of Cr-N coatings on 316H stainless steel via pack chromizing and gas nitriding, and their resistance to liquid metal corrosion in early stages

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 PbBi. 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.

Lead-bismuth eutectic corrosion resistance of TiAlN coating after N5+ ion irradiation

In this study, a Ti0.33Al0.67N coating with Cr as the transition layer was prepared by cathodic arc-ion plating. After irradiation with N5+ ions, the coating was exposed to lead-bismuth eutectic (LBE) at 450 °C for 3000 h. The effect of irradiation on the corrosion resistance of the coatings was also investigated. No evidence of an LBE corrosion attack was observed in either the irradiated or unirradiated coatings. Transmission electron microscopy images revealed that the nanoscale oxide layer on the surface of the titanium aluminum nitride coating was the main barrier to LBE corrosion. The unirradiated coating had a single oxide layer, whereas the irradiated coating had a double oxide layer. Irradiation also affects the coating adhesion by inducing stress. However, after the corrosion test, the adhesion of all coating samples unexpectedly increased and were almost at the same level. The coating exhibited excellent properties after irradiation and LBE corrosion; therefore, the coating can be applied in future nuclear reactors.

Study on the corrosion behavior of laser surface remelted and laser cladding of ferritic/martensitic steels after exposure to lead-bismuth eutectic at 700 °C

This study explores two vital structural materials, T91 (Fe-9Cr) and SIMP (Fe-11Cr) steels, in the context of lead-cooled fast reactors and accelerator-driven sub-critical systems (ADS). Lead-bismuth eutectic (LBE) functions as a key coolant and spallation target material due to its impressive thermal conductivity, neutron yield, and chemical properties. Unfortunately, materials in contact with LBE are prone to severe corrosion at elevated temperatures (T>500 °C), compromising their integrity. To bolster corrosion resistance, we utilized laser remelting and laser cladding to apply FeCrAl/TiN coatings on the steel surfaces. Our study scrutinizes the corrosion behavior of steel in LBE saturated with oxygen at 700 °C and investigates the underlying causes. Following 240 h of exposure to corrosion, T91 and SIMP steels subjected to laser remelting displayed substantial oxide scale formation. Lead-bismuth atoms infiltrated the outer oxide layer (Fe3O4), diminishing adhesion between the inner and outer oxide layers, leading to the detachment of the outer oxide layer. The inner oxide layers, composed of Fe-Cr spinel, were approximately 123 μm thick for T91 steel and 77 μm for SIMP steel, underscoring SIMP steel's superior corrosion resistance. For T91 steel treated with laser cladding FeCrAl/TiN coating, a characteristic duplex oxide layer with a total thickness of around 83 μm was formed, with noticeable deposition of Pb-Bi atoms at the interface between the outer and inner oxide layers. Conversely, only a protective alumina layer safeguarded SIMP steel from LBE corrosion. This outcome emphasizes the efficacy of laser cladding FeCrAl/TiN coating in providing superior protection for SIMP steel over T91 steel. Our research significantly contributes to the development of anti-corrosion coatings for high-temperature LBE environments.

Corrosion behavior of AFA steel in lead-bismuth eutectic alloy with saturated oxygen at 500°C

Alumina-forming Austenitic (AFA) steel is one of the candidate corrosion-resistant structural materials for lead-cooled fast reactors, exhibiting excellent high-temperature corrosion resistance. However, its corrosion mechanisms in lead-bismuth eutectic (LBE) environment at the design operating temperature of lead-cooled fast reactors have not been fully elucidated. In this study, AFA steel was immersed in static LBE with saturated oxygen at 500 °C for 3000 hours. The corrosion behavior of AFA samples was obtained by analyzing the morphology of corrosion cross section and the distribution of elements. The results showed that the AFA steel did not form an oxide film that could effectively resist LBE. Dissolution corrosion of the matrix becomes more severe the longer the exposure time. When the NiAl phase in the matrix is located at the surface, oxide nodules are generated. It has a double-layer oxide structure, which has better resistance to LBE corrosion. Nb undergoes oxidative rupture and has a tendency to detach from the surface of the substrate when it is located on the surface. Cracks occur on the surface of the matrix after 3000 hours of corrosion, and LBE penetrates into the matrix along the cracks.

First-principles study on the corrosion resistance of iron oxide surface and grain boundary in austenitic steel to lead–bismuth eutectic

In this paper, the corrosion properties of austenitic steel with and without protection of Fe3O4 scale was investigated based on first-principles calculations. The results show that lead–bismuth eutectic (LBE) is only adsorbed at some local positions on Fe3O4 scale, but is stably adsorbed at various sites on the Fe surface. The adsorption of LBE reduces the escape energy of Fe on Fe3O4 scale and pure Fe surface, and pure Fe surface is more susceptible to LBE corrosion. Moreover, the interaction between common alloying elements (Ni, Cu, Mo, Mn, Cr, Nb, V, Si, and Al) and oxygen atoms are investigated. Among them, Ni and Cu are weakly bound to O and most prone to escape from the Fe3O4 scale. Mo, Mn, and Cr have a significant escape tendency, while Nb, V, Si, and Al are not susceptible to escape. LBE will embrittle the grain boundary (GB) under failure of oxide layer. Ti, Cr and Ni all improve the strength of the GB structure, but the strengthening effect is limited, and GB embrittlement is dominated by Pb and Bi.

The effects of Si‐ion implantation and preoxidation on the corrosion behavior of a new steel SIMP in 550∘C ${\bf{55}}{{\bf{0}}}^{\circ }{\bf{C}}$ lead‐bismuth eutectic

AbstractTo improve the corrosion resistance of SIMP steel, we have investigated Si‐ion implantation and preoxidation effects on the corrosion behavior of SIMP steel samples, which have been in stagnant lead‐bismuth eutectic (LBE) with saturated oxygen at C for 1000 h. It was found that increasing Si content on the surface did not improve corrosion resistance performance. By contrast, the preoxidized sample demonstrated high resistance to LBE corrosion due to the presence of a thin Cr‐enriched oxide layer.

Microstructure, mechanical properties and lead-bismuth eutectic corrosion behavior of FeCrAlTiNb high-entropy alloy coatings

The FeCrAlTiNb high-entropy alloy coatings are fabricated by magnetron sputtering method to prevent the lead-bismuth eutectic (LBE) corrosion of structural components used in lead-cooled fast reactors, and their microstructure, mechanical properties and LBE corrosion behavior are investigated systematically. The coatings exhibit significantly improved hardness, creep and wear resistance compared with ferritic/martensitic (F/M) steel. Moreover, the coatings show promising LBE corrosion resistance with parabolic oxidation rate constant 3–5 orders of magnitude lower than other candidate steels, which is ascribed to their intrinsic amorphous structure and the formation of protective FeCr2O4/Cr2O3 double-layer. Finally, the growth of oxide scale is discussed in detail.

Effect of Au-ion irradiation on the morphology, microstructure and lead-bismuth eutectic corrosion behavior of refractory TiNbZrMoV high-entropy alloy coating

The effect of Au-ion irradiation on the morphology, microstructure and lead-bismuth eutectic (LBE) corrosion behavior of refractory TiNbZrMoV high-entropy alloy coating was investigated. After irradiation, the surfaces of coatings were smoothened, and crystalline phase was formed in the coatings. After LBE corrosion at 650 °C, the irradiated samples presented a triple layer (interface Fe-Cr spinel, coating and surface Fe-oxide layer) consistent with the pristine sample, and the coating still maintained the low-consumption characteristic. Irradiation accelerated LBE corrosion, which could be attributed to the formation of grain boundary and defects that provided more diffusion channels for atoms.

Transient analyses for China initiative Accelerator Driven System using the extended BELLA code

China initiative Accelerator Driven System (CiADS) is a 10 MW lead–bismuth eutectic (LBE) cooled subcritical reactor loaded with UO2 fuels in the first phase, which is designed to demonstrate the engineering feasibility of the ADS concept. The transient analyses were performed to show the safety potential and dynamic characteristics of the CiADS subcritical reactor using the extended BELLA code. Typical scenarios, such as beam-trip transients, unprotected beam overpower (UBOP), unprotected and protected loss of flow (ULOF and PLOF), unprotected and protected loss of heat sink (ULOHS and PLOHS) and self-defined station blackout (SBO), were analyzed and simulated. The results indicate that, as a low-power reactor, the CiADS subcritical reactor has a large margin to avoid severe damage in the core. Short-term cladding failure caused by thermal fatigue under frequent beam trips may not happen since the variations of temperatures are relatively small. However, accelerated LBE corrosion combined with accumulated creep tends to be a risk under ULOF and ULOHS.

Microstructure, mechanical properties and lead-bismuth eutectic corrosion behavior of (AlCrFeTiMo)NO and (AlCrFeTiNb)NO high entropy metal sublattice ceramic coatings

The (AlCrFeTiMo)NO and (AlCrFeTiNb)NO high entropy metal sublattice ceramic coatings were specially designed and deposited on 12Cr F/M steel substrate by means of reactive magnetron sputtering technology. The microstructure, mechanical properties and lead-bismuth eutectic (LBE) corrosion resistance of the coatings were investigated systematically. Both the coatings exhibited a single NaCl-type FCC solid solution structure. The (AlCrFeTiNb)NO coating displayed higher nanohardness (21.5 GPa), reduced elastic modulus (292.9 GPa) and compressive residual stress (−1650 MPa). The (AlCrFeTiMo)NO coating exhibited the better LBE corrosion resistance with lower oxidation corrosion rate relative to the (AlCrFeTiNb)NO coating, but some large-sized penetrating cracks appeared after corrosion. This study not only suggested that the high entropy metal sublattice ceramic coatings could be promising candidates for the protection of structural materials or fuel cladding in the next generation lead based reactors, but also provided basic information for designing better high entropy metal sublattice coatings, especially avoiding the inclusion of the high quantity and content of non-nitride-forming elements such as Fe.

Effects of Y2O3 Addition on the Microstructure and Static Lead-Bismuth Eutectic Thermal Corrosion Behaviors of FeCrAlTiC-xY2O3 Laser Clade Coatings

In order to prevent the lead-bismuth eutectic (LBE) corrosion of stainless-steel components used in nuclear reactors, the FeCrAlTiC-xY2O3 coatings were prepared on 304 stainless steel (304SS) by laser cladding. After adding Y2O3, Y2TiO5 and Y2Ti2O7 formed, which have a combined strengthening effect on improving hardness. The 0.2 wt.% Y2O3 coating showed the highest hardness as ~489 HV. In the 400 °C wear test, the weight loss of coating samples was less than ~5.2 mg, while the weight loss of 304SS samples was ~35.5 mg. The 0 wt.% Y2O3 coating showed the highest wear resistance, indicating that adding Y2O3 could result in the decrease of wear resistance. The LBE corrosion behaviors of coatings at 500 °C were investigated. The results showed that a uniform and dense oxide scale with a low growth rate was obtained on the coating surface, and no penetration of LBE into the coating was observed. After 1000 h of corrosion, the oxide scale of coatings grew to merely a ~0.3 μm thickness. The corrosion resistance mechanism of the coating in oxygen-saturated LBE at 500 °C was proposed based on experimental results along with a thermodynamic and kinetic analysis.

Effect of minor addition of Ce on microstructure and LBE corrosion resistance for CLAM steel

Ce-CLAM specimens were exposed to lead-bismuth eutectic (LBE) for 1500 h under 10−6 wt% oxygen concentration at 500 °C. The continuity and integrity of the oxide scale were better in Ce-CLAM specimens than in CLAM specimens, and the parabolic rate constant kp of oxide scale growth was only about 1/2 that of CLAM specimens. Ce-CLAM specimens exhibited better LBE corrosion resistance compared with CLAM specimens, which was mainly attributed to the inhibition function for Fe out-diffusing and the improvement for grain boundaries from Ce. A model was proposed to illustrate the mechanism of Ce-CLAM’s LBE corrosion resistance.