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Accident Tolerant Fuels (ATF) have emerged as a promising solution to improve safety during reactor accidents by enhancing fuel performance in light water reactors (LWRs). This paper investigates the performance of different ATF concepts, including Chromium-coated Zircaloy (CrZry), advanced steel (FeCrAl), and Silicon Carbide (SiC) as cladding materials, paired with Uranium Dioxide (UO 2 ), Uranium Silicide (U 3 Si 2 ), and Uranium Nitride (UN) fuels, under spectrum shift regulation conditions in a VVER-S reactor. Using the GETERA program, a series of calculations were conducted to compare multiplying factors and isotopic concentrations under spectrum-shifted conditions. The results demonstrate significant differences in fuel cycle characteristics and isotopic behavior, with SiC emerging as the optimal cladding material for maximizing neutron economy and minimizing parasitic absorption.

Silicon carbide composites are expected for light water reactors. The objective is to understand the steam oxidation behavior and the high-temperature water corrosion behavior of the liquid phase sintering silicon carbide and to develop the liquid phase sintering silicon carbide composites, which are stable at the high-temperature water conditions in normal operation and the high-temperature steam conditions in a severe accident. The steam oxidation experiments were carried out at 1200 and 1400 °C. The high-temperature water corrosion experiments were carried out at 320 and 360 °C. The formation of the silicate, which is expected to have excellent resistance to the steam, was confirmed following the steam exposure at 1400 °C. High-temperature water corrosion resistance was improved by the formation of Yttrium Aluminum Garnet at the grain boundary. The particle-dispersion silicon carbide composite tubes with the modified condition were developed, and the thermal shock experiments from 1200 °C to ambient temperature were carried out. The composite tubes showed excellent oxidation and thermal shock resistance. The particle-dispersion liquid phase sintering silicon carbide composites with the modified condition are promising materials for light water reactors.

Titanium alloys are widely used in various structural materials due to their lightweight properties. However, the low wear resistance causes significant economic losses every year. Therefore, it is necessary to implement wear-resistant protection on the surface of titanium alloys. In this study, four types of in situ composite ceramic coatings with two-layer gradient structures were prepared on a Ti-6Al-4V (TC4) substrate using laser cladding. In order to reduce the dilution rate, a transition layer (Ti-40SiC (vol.%)) was first prepared on TC4 alloy. Then, a high-volume-fraction in situ composite ceramic working layer (Ti-xFe-80SiC (vol.%)) with different contents of Fe-based alloy powder (x = 0, 5, 10 and 15 vol.%) was prepared. The working surface of Ti-40SiC (TL) exhibited a typical XRD pattern of Ti, TiC, Ti5Si3, and Ti3SiC2. In comparison, both Ti-80SiC (WL-F0) and Ti-5Fe-80SiC (WL-F5) exhibited similar phase compositions to the TL coating, with no new phase identified in the coatings. However, the TiFeSi2 and SiC phases were presented in Ti-10Fe-80SiC (WL-F10) and Ti-15Fe-80SiC (WL-F15). It is proven that the addition of the Fe element could regulate the in situ reaction in the original Ti-Si-C ternary system to form the new phases with high hardness and good wear resistance. The hardness of the WL-F15 (1842.9 HV1) is five times higher than that of the matrix (350 HV1). Due to the existence of self-lubricating phases such as Ti5Si3 and Ti3SiC2, a lubricating film was presented in the WL-F0 and WL-F5 coatings, which could block the further damage of the friction pair and enhance the wear resistance. Furthermore, a wear-transition phenomenon was observed in the WL-F10 and WL-F15 coatings, which was similar to the friction behavior of structural ceramics. Under the load of 10 N and 20 N, the wear volume of WL-F15 coating is 5.2% and 63.7% of that in the substrate, and the depth of friction of WL-15 coating is only 14.4% and 80% of that in the substrate. The transition of wear volume and depth can be attributed to the wear mechanism changing from oxidation wear to adhesive wear.

Cr3C2-modified NiCr–TiC composite coatings were prepared using the plasma spraying technique for different Cr3C2 contents on the microstructure and the properties of the Ni-based TiC cladding layer were investigated. The microstructures of the coatings were characterized using scanning electron microscopy, and the friction and wear performance of the coating was evaluated by the wear tests. The results revealed that the surfaces of the Cr3C2-modified NiCr–TiC composite coatings with varying Cr3C2 contents were dense and smooth. TiC was uniformly distributed throughout the entire coating, forming a gradient interface between the binder phase of the Ni-based alloy and the hard phase of TiC. At high temperatures, Cr3C2 decomposes, with some chromium diffusing and forming complex carbides around TiC, some chromium solubilizes with Fe, Ni, and other elements. An increase in chromium carbide content leads to an upward trend in hardness. The measured hardness of the coatings ranged from 600 to 850 HV3 and tended to increase with increasing Cr3C2 content. When the mass fraction of Cr3C2 reached 30%, the hardness increased to 850 HV3, and the cracks and defects were observed in the coating, resulting in a wear resistance decline.

A microwave hybrid heating technique has been employed to develop NiCr-Mo-SiC composite cladding on titanium alloy (Grade-5/Ti-6Al-4 V/Titan-31). The developed claddings have been characterized for microstructural features, phase analysis, microhardness measurements, and 3D optical profile parameters by employing scanning electron microscopy, x-ray diffraction, Vickers microhardness tester, and 3D optical profilometer, respectively. Microwave clads have been subjected to linear reciprocator ball on plate wear test with static alumina indenter. Wear track parameters and friction coefficients have been studied. A dense microstructure with uniform distribution of hard phases and good metallurgical bonding with no visible pores and cracks has been obtained. Cladding exhibits nearly 2 times higher hardness than the base alloy. Coefficient of friction studies revealed that higher molybdenum content enhances internal lubricity.

Due to its several advantages, laser cladding has been used to enhance the surface properties of parts subjected to severe loading conditions. Despite its benefits, the performance and quality characteristics of the coatings produced depend highly on the complex relationship between the coating materials and the process variables. Hybrid reinforcements such as TiC and SiC in metal matrix composites can provide synergistic benefits for components used in extreme environments, like mining, by significantly enhancing wear resistance and mechanical properties. In this work, the effect and many-objective optimisation of the laser processing variables were carried out on TiC/SiC/16MnCr5 multi-track composite coating on A514 steel. By employing hybrid response surface modelling (RSM) and non-dominated sorting genetic algorithm III (NSGA III), the effect of scanning speed (S), powder feed rate (F), and laser power (P) on coating aspect ratio, dilution, microhardness, and wear resistance were investigated and optimised. The influence of the process variables on aspect ratio, dilution, microhardness, and wear volume loss are in this order, respectively: S > P > F; S > F > P; P > F > S; and P > S > F. The interaction of the process parameters was significant. The wear resistance and microhardness were enhanced due to the partial dissolution of carbides in the matrix. Based on the NSGA III optimisation, the optimal process parameters identified were P  = 1550 W, S  = 500 mm/min, and F  = 7 g/min. The validation experiment revealed a close agreement with the predicted results, with errors of less than 5% for all the objectives. The optimised coating’s microstructure consisted predominantly of columnar crystals with minor regions of equiaxed dendrites. Compared to the substrate, the optimised coating’s microhardness improved by 350%, while its compressive strength was enhanced by 41%.

The main objective of this study was to develop a metal matrix composite (MMC) coating on Ti-6Al-4V substrate using a laser cladding method with coaxial powder feeding system. This study investigated the effectiveness of a novel material combination of Ni60 alloy and SiC ceramic in improving the surface properties of titanium alloys. The coatings were analyzed for their phase composition, microstructure, and elemental distribution. The microhardness, tribological properties, and wear mechanism of the coatings were evaluated using a Vickers microhardness tester and a ball-on-disk sliding test under dry conditions. The laser clad coatings consisted mainly of TiC, TiC+TiB eutectic, Cr7C3, Ni3Ti, and γ-Ni. The MMC coatings demonstrated significantly improved microhardness values, wear resistance, and tribological properties compared to those of the titanium substrates, due to the in situ generation of hard particles and dispersion strengthening of the supersaturated solid solution. However, excessive SiC content resulted in increased friction coefficient, instability, and irregular wear characteristics due to brittle debonding on the wear surface. This study identified the optimal combination ratio of Ni60 and SiC powder for improving the performance of the MMC coating and proposed future research directions for further enhancing the coating properties.

Laser cladding technology is used to apply two types of coatings, Inconel 625 and Inconel 625 + 20% WC, onto duplex stainless steel 2507. A comprehensive comparison is made on the hardness, wear resistance, and corrosion resistance between the substrate material and the two coatings. Additionally, a detailed analysis of their friction and corrosion mechanisms is conducted. The results indicate that the addition of WC effectively refines the grain size and increases the coating’s compactness, leading to a 38.5% hardness improvement in the Inconel 625 + 20% WC coating compared to the substrate. Regarding friction and corrosion performance, the Inconel 625 + 20% WC coating exhibits the highest friction coefficient and the lowest wear volume, demonstrating superior wear resistance. Furthermore, the wear morphology of the Inconel 625 + 20% WC coating is the most uniform, featuring a smaller damage area and minimal tribo-corrosion damage. In electrochemical static tests, the Inconel 625 coating exhibits the best corrosion resistance, followed by the Inconel 625 + 20% WC coating and the 2507 substrate. The high nickel content in the Inconel 625 coating contributes to its excellent corrosion resistance. However, the addition of WC slightly decreases the corrosion resistance but significantly improves friction performance.

A microwave hybrid heating technique was applied to produce the NiCr-Mo-SiC composite cladding on Titan-31. The developed claddings were tested for microstructural features, phase analysis, microhardness, and surface roughness parameters using scanning electron microscopy (SEM), X-ray diffraction (XRD), Vickers Microhardness, and 3D optical profilometers, respectively. Using a static alumina indenter on microwave clads, the linear reciprocator ball on plate wear test was performed. Both friction and wear track metrics have been studied. A dense microstructure without observable holes or fractures has been achieved, together with a homogeneous distribution of hard phases and strong metallurgical bonding. Cladding is typically three times tougher than the underlying metal. Due to the formation of hard carbide phases, which increased hardness and internal lubricity, cladding has a lower coefficient of friction than the substrate.

The complex multiscale and anisotropic nature of silicon carbide (SiC) ceramic matrix composite (CMC) makes it difficult to accurately model its performance in nuclear applications. The existing models for nuclear grade composite SiC do not account for the microstructural features and how these features can affect the thermal and structural behavior of the cladding and its anisotropic properties. In addition to the microstructural features, the properties of individual constituents of the composites and fiber tow architecture determine the bulk properties. Models for determining the relationship between the individual constituents’ properties and the bulk properties of SiC composites for nuclear applications are absent, although empirical relationships exist in the literature. Here, a hierarchical multiscale modeling approach was presented to address this challenge. This modular approach addressed this difficulty by dividing the various aspects of the composite material into separate models at different length scales, with the evaluated property from the lower-length-scale model serving as an input to the higher-length-scale model. The multiscale model considered the properties of various individual constituents of the composite material (fiber, matrix, and interphase), the porosity in the matrix, the fiber volume fraction, the composite architecture, the tow thickness, etc. By considering inhomogeneous and anisotropic contributions intrinsically, our bottom-up multiscale modeling strategy is naturally physics-informed, bridging constitutive law from micromechanics to meso-mechanics and structural mechanics. The effects that these various physical attributes and thermo-physical properties have on the composite’s bulk thermal properties were easily evaluated and demonstrated through the various analyses presented herein. Since silicon carbide fiber-reinforced SiC CMCs are also promising thermal–structural materials with a broad range of high-end technology applications beyond nuclear applications, we envision that the multiscale modeling method we present here may prove helpful in future efforts to develop and construct reinforced CMCs and other advanced composite nuclear materials, such as MAX phase materials, that can service under harsh environments of ultrahigh temperatures, oxidation, corrosion, and/or irradiation.