Carbide Matrix Research Articles

Ablation behavior of medium entropy carbide ceramics with different molar ratios of (Hf, Zr, Ti)C in oxyacetylene flame

(Hf1/3Zr1/3Ti1/3)C and (Hf1/2Zr1/3Ti1/6)C middle-entropy carbide ceramics were successfully prepared using polymer-derived ceramic method. The study examines the microstructural evolution, phase composition changes, and ablation behavior of these two ceramic materials when subjected to an oxyacetylene flame at varying heat fluxes. The experimental results indicate that at a heat flux of 5 MW/m2, the mass and linear ablation rates of (Hf1/3Zr1/3Ti1/3)C ceramic are -0.837 mg/s and 1.857 μm/s, respectively. In contrast, (Hf1/2Zr1/3Ti1/6)C ceramic exhibits significantly superior ablation resistance, with rates of -0.315 mg/s and -0.745 μm/s. This underscores the critical role of compositional adjustments in enhancing the ablation performance of the ceramic. During ablation, (Hf1/2Zr1/3Ti1/6)C forms an optimal amount of (Hf, Zr)TiO4 healing phase, which contributes to the development of a stable oxide film consisting of an m-(Hf, Zr, Ti)O2 oxide skeleton and a (Hf, Zr)TiO4 liquid phase. This structure effectively resists high-velocity airflow erosion and oxygen penetration. Additionally, the formation of a carbonaceous oxide interlayer strengthens the bond between the oxide layer and the carbide matrix, further improving the material's ablation resistance. The study highlights the significant influence of compositional ratio control on the ablation behavior and mechanisms of carbide ceramics, providing a robust foundation for their application in high-temperature thermal protection technologies.

Study on the circumferential tensile behavior of SiCf/SiC composite cladding tubes across a broad temperature range: High temperature interface enhancement effect from a cross-scale perspective

In nuclear reactors, Silicon carbide fiber reinforced silicon carbide matrix (SiCf/SiC CMC) cladding tubes are susceptible to circumferential damage due to internal gas pressure expansion. However, due to its complex spatial fiber winding structure, investigating circumferential tensile failure under extreme temperatures is challenging. Therefore, using cross-scale methods and experiments from 20 °C to 1100 °C, this study examined circumferential damage at macro, micro, and nanoscale levels. Specifically, as the temperature increases, the material still maintains excellent structural stability; at 1100 °C, the critical damage load decreases by 72.5 % and the critical displacement increases by 197.1 %.The " interface enhancement effect" between the fibers and matrix results in a relatively smooth fracture morphology. At the macroscopic level, morphology evolution reflects the transition from brittle to pseudo-plastic behavior. Additionally, based on the principle of minimum potential energy and the theory of semi-geodesics, the complex macroscopic structure and microscopic Representative Volume Element (RVE) model was reconstructed. The findings show the numerical model accurately represents the circumferential damage of SiCf/SiC CMC under extreme temperatures. Simultaneously, at the molecular level, the interfacial strength at high temperature is 7.5 % higher than that at ordinary temperature, resulting in a distinct adhesive interaction between matrix and fibers. This study opens up new avenues for the fundamental theoretical research of such ceramic matrix materials. interface enhancement effect.

The Bimodal Epithermal Astronuclear Reactor (BEAR): A Long-Lived, Universal Space Nuclear Powerplant

A neutronic model of a Nuclear Thermal Propulsion reactor based on the NERVA Peewee design using High Assay Low Enriched Uranium (HALEU) fuel in a Zirconium Carbide matrix has been thoroughly characterised and continuously modified over the last few years at the CSNR. The initial design (Emu, for the flightless bird) created in the summer of 2020 and presented at the NETS 2021 conference, has undergone significant adjustments in this time. Two major investigations have been undertaken and evolved over time; one into the requisites for the provision of electrical power to the propelled spacecraft via the circulation of a noble gas mixture in a closed Brayton cycle, and another into the use of planetary regolith as a reflector, reducing neutron leakage at what would otherwise be the reactor’s end of life in vacuo, rekindling it for an extended period of time as well as providing a very easy ultimate disposal solution, replacing the control drums with rods. It was determined that there are no insurmountable obstacles to performance in either mode.

Influence of Carbon Content on Element Diffusion in Silicon Carbide-Based TRISO Composite Fuel

The coating layers of Tri-structural Isotropic Particles (TRISO) serve to protect the kernel and act as barriers to fission products. Sintering aids in the silicon carbide matrix variably react with TRISO coating layers, leading to the destruction of the coating layers. Investigating how carbon content affects element diffusion in silicon carbide-based TRISO composite fuel is of great significance for predicting reactor safety. In this study, silicon carbide-based TRISO composite fuels with different carbon contents were prepared by adding varying amounts of phenolic resin to the silicon carbide matrix. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) were employed to characterize the phase composition, morphology, and microstructure of the composite fuels. The elemental content in each coating layer of TRISO was quantified using Energy-Dispersive X-ray Spectroscopy (EDS). The results demonstrated that the addition of phenolic resin promoted the uniform distribution of sintering aids in the silicon carbide matrix. The atomic percentage (at.%) of aluminum (Al) in the pyrolytic carbon layer of the TRISO particles reached its lowest value of 0.55% when the phenolic resin addition was 1%. This is because the addition of phenolic resin caused the Al and silicon (Si) in the matrix to preferentially react with the carbon in the phenolic resin to form a metastable liquid phase, rather than preferentially consuming the pyrolytic carbon in the outer coating layer of the TRISO particles. The findings suggest that carbon addition through phenolic resin incorporation can effectively mitigate the deleterious reactions between the TRISO coating layers and sintering aids, thereby enhancing the durability and safety of silicon carbide-based TRISO composite fuels.

The combined effects of carbides and martensite blocks heterogeneity on the fatigue life scatter in bearing steel

With the mitigation of inclusion-related harm through purifying methods, the fatigue life scatter of bearing steels is now predominantly governed by microstructural heterogeneity. This work employs an integrated experimental-numerical approach to elucidate the microstructure-related localized plastic strain in 52100 bearing steel under cyclic loading. We observed significant localized plastic strain in the coarse grains adjacent to aggregated carbides after unloading, which may act as a precursor to fatigue cracks and contribute to fatigue life scatter. This strain arises from two primary factors: stress concentration due to aggregated carbides and the relatively lower strength of coarse matrix grains, which is usually overlooked. Enhancing the homogeneity of both carbide distribution and matrix grain size will be a strategy to reduce the fatigue life scatter of bearing steels.

Anionic vacancy filled-up mechanism in (Ti0.2V0.2Nb0.2Ta0.2W0.2)Cx high-entropy carbide

Carbothermic reduction for high-entropy carbide preparation has it’s promising potential for industrialization application and the relevant basic theory for formation process required to clarify urgently. This research reports the anionic vacancy filled-up (AVF) mechanism during the formation of (Ti0.2V0.2Nb0.2Ta0.2W0.2)Cx high-entropy carbide powder by predictions of first-principles calculations, thermodynamic phase diagram calculations and verification by experimental preparation and characterization. The mechanism demonstrated that the rock-salt carbide matrix with superfluous anionic vacancy was formed firstly and the residual carbon substance continuously occupied the vacancies to an equilibrium state. The origin of the equilibrium anionic vacancy concentration was revealed from the perspective of the energy variation.

Removal mechanism and hole quality of SiCp/Al composites by ultrasonic elliptical vibration-assisted helical milling

SiCp/Al composites are widely used in the aerospace field due to their excellent properties. However, the huge difference in the properties of silicon carbide and aluminum matrix materials can easily lead to machining defects. Ultrasonic vibration-assisted machining is an effective method to deal with difficult-to-machine materials. In this study, ultrasonic elliptical vibration is applied to the helical milling of SiCp/Al composites. Firstly, the ultrasonic elliptical vibration-assisted helical milling (UEVHM) cutting-edge trajectory is modeled, and the equation of the UEVHM tool-chip separation condition is established, which lays a foundation for the analysis of the cutting mechanism. Then, the influence of ultrasonic elliptical vibration on the removal mechanism of SiCp/Al composites was investigated by finite element simulation. It was found that UEVHM can reduce the tearing of aluminum matrix and reduce the hole damage by changing the direction of the cutting velocity and the relative position of the cutting edge and particles. Finally, the single-factor experiment was carried out, and the surface morphology and roughness of HM and UEVHM were compared. The influence of process parameters on the surface roughness of UEVHM was analyzed. The experimental results show that compared with HM, UEVHM can reduce surface defects and exit damage, to obtain better surface roughness and exit edge quality. The increase in cutting speed can reduce the roughness, and the increase in pitch and revolution speed will increase the surface roughness.

Modular gas-cooled reactor core optimal design and additive manufacturing performance based on SiC matrix dispersed with TRi-structural ISOtropic fuel

High-temperature gas-cooled reactors present significant technical competitiveness in various fields, such as low-carbon electricity, thermal energy, and hydrogen supply. Silicon Carbide (SiC) matrix dispersed with TRi-structural ISOtropic (TRISO) particle fuel is characterized by high-temperature tolerance, radiation resistance, and good neutron economy, which has emerged as a pivotal technological pathway for reactor core design. With the rapid advancement of SiC Additive Manufacturing (AM) technology, there is a substantial increase in core design flexibility, and an innovative gas-cooled reactor design was proposed by Monte Carlo (MC) method in this paper. The Non-uniform Rational B-spline (NURBS), Latin Hypercube Sampling (LHS), second-order polynomial response surface, as well as Genetic Algorithm (GA) were coupled to realize the optimization design for the coolant channel. Besides, a modular fuel design was proposed, and the AM SiC shell was fabricated using Binder Jetting (BJ) technology. Furthermore, the densification of the AM SiC shell and the matrix with SiC powder and SiC microspheres (TRISO simulator) was investigated by Chemical Vapor Infiltration (CVI). Finally, the microscopic morphology analysis and thermal-mechanical performance characterization of the samples were conducted, which demonstrated the technical feasibility and advanced capabilities of the SiC matrix dispersed with TRISO fuel based on AM technology.

Experimental investigation of the microstructural and wear behaviours of silicon carbide and boron nitride-reinforced AZ91D magnesium matrix hybrid composites

Experimental investigation of the microstructural and wear behaviours of silicon carbide and boron nitride-reinforced AZ91D magnesium matrix hybrid composites

Radio frequency‐assisted zirconium carbide matrix deposition for continuous fiber‐reinforced ultra high temperature ceramic matrix composites

AbstractZirconium carbide (ZrC) is considered to be a potential candidate for ultra high temperature applications due to its high melting point, good chemical inertness, and ablation resistance, but the monolithic form suffers from low fracture toughness and hence poor thermal shock resistance. Reinforcing it using continuous carbon fibers (Cf) to create an ultra high temperature ceramic matrix composite is an obvious solution, however densifying ZrC requires the use of very high temperatures combined with significant pressure, such as obtained by using hot pressing or spark plasma sintering, which risks damaging fibers. In the present work, radio frequency‐assisted chemical vapor infiltration (RF‐CVI) has been investigated with a view to forming Cf/ZrC composites. These initial experiments revealed the ability to deposit pure, nano‐grained, and near stoichiometric ZrC with deposition occurring preferentially from the center of the sample due to the nature of the inverse temperature profile developed. The deposited ZrC grains were in the range of 4–9 nm in size and had a lattice parameter of 0.4750 nm. The work also showed that the use of RF‐CVI enabled the minimization of early pore sealing, a common problem for conventional CVI.

Mechanical Properties of Silicon Carbide Composites Reinforced with Reduced Graphene Oxide.

This article presents research on the influence of reduced graphene oxide on the mechanical properties of silicon carbide matrix composites sintered with the use of the Spark Plasma Sintering method. The produced sinters were subjected to a three-point bending test. An increase in flexural strength was observed, which reaches a maximum value of 503.8 MPa for SiC-2 wt.% rGO composite in comparison to 323 MPa for the reference SiC sample. The hardness of composites decreases with the increase in rGO content down to 1475 HV10, which is correlated with density results. Measured fracture toughness values are burdened with a high standard deviation due to the presence of rGO agglomerates. The KIC reaches values in the range of 3.22-3.82 MPa*m1/2. Three main mechanisms responsible for the increase in the fracture toughness of composites were identified: bridging, deflecting, and branching of cracks. Obtained results show that reduced graphene oxide can be used as a reinforcing phase to the SiC matrix, with an especially visible impact on flexural strength.

Influence of TiB2 Incorporation on Microstructural Evolution in Laser-Clad FeCrV15 + TiB2 Deposits

Vanadium carbide (VC)-reinforced Fe-based hard facings are pivotal in enhancing the wear resistance of tools prone to mechanical damage. This study investigates the impact of titanium diboride (TiB2) addition (at varying laser power and powder federate) on the microstructure, hardness, wear resistance, and corrosion resistance of high-carbon ferrochrome FeCrV15 clad coatings for agricultural and mining applications. Laser cladding techniques were employed to deposit coatings on steel substrates, and the samples were subjected to comprehensive material characterization, including microhardness testing, wear studies, and electrochemical polarization. Results reveal that TiB2 addition led to visible reactions during deposition, resulting in decreased hardness compared to pure FeCrV15 coatings. Moreover, TiB2 incorporation adversely affected the anti-corrosion properties of the coatings, although FeCrV15 coatings exhibited superior corrosion resistance compared to FeCrV15 + TiB2 coatings. Tribological evaluations showed that all coatings exhibited better anti-wear capabilities compared to the steel substrate, with varying degrees of improvement influenced by TiB2 concentration and laser beam power. Overall, FeCrV15 deposits demonstrated superior anti-wear and anti-corrosion properties compared to FeCrV15 + TiB2 coatings and attributed to increased convergence of carbide particles and higher grain-boundary density. This research contributes to understanding the intricate interplay between carbide reinforcement and matrix structure in Fe-based hard facings, providing insights for optimizing coating performance in demanding industrial applications.

Analysis of gas-cooled micro modular reactor (MMR) fuel

The gas-cooled micro modular reactor (MMR) is a novel concept with a compact fuel form consisting of thousands of tri-isotropic fuel (TRISO) particles dispersed in a silicon carbide matrix. The MMR fuel has a high volume packing fraction and is horizontally placed within graphite channels. This study demonstrates that the horizontal arrangement of MMR fuel within graphite channels resulted in a non-uniform gap between the fuel and graphite brick, leading to an "off-center" temperature distribution within the fuel, and resulting in differences in TRISO performance even within sub-zones positioned symmetrically in the radial direction. Given the complexity of the fuel structure and the challenges involved in simulation, a multi-scale and multi-physics coupled analysis method of MMR fuel was realized in this work by implementing physical models into the open-source finite element platform MOOSE. Thermal-mechanical analysis and failure analysis within sub-zones of the typical design MMR fuel during normal operation were conducted through simulation. The results indicate that higher-temperature sub-zones exhibit increased internal pressure within TRISO and show greater tensile stress in the Chemical Vapor Deposited Silicon Carbide (CVD-SiC) layer. Regarding fuel failure analysis, this work found limited impact from Pd penetration and kernel migration. Pressure-induced particle failure, closely associated with stress in CVD-SiC, emerges as the primary failure criterion. The probability of fuel failure is relatively low, and interfacial cohesive parameters have an impact on the SiC stress and the fuel failure probability at the highest level.

Investigation of High-Speed Rubbing Behavior of GH4169 Superalloy with SiC/SiC Composites

The silicon carbide fiber-reinforced silicon carbide matrix (SiC/SiC), ceramic matrix composite (CMC) and nickel-based superalloy GH4169 can be utilized in high-temperature applications due to their high-temperature performance. The SiC/SiC composites are commonly used in turbine outer rings, where they encounter friction and wear against the turbine blades. This high-speed rubbing occurs frequently in aircraft engines and steam turbines. To investigate the tribological behavior of these materials, rubbing experiments were conducted between the SiC/SiC and the GH4169 superalloy. The experiments involved varying the blade tip speeds ranging from 100 m/s to 350 m/s and incursion rates from 5 μm/s to 50 μm/s at room temperature. Additionally, experiments were conducted at high temperatures to compare the tribological behavior under ambient conditions. The results indicated that the GH4169 superalloy exhibited abrasive furrow wear during rubbing at both room temperature and high temperature. Furthermore, at elevated temperatures, some of the GH4169 superalloy adhered to the surface of the SiC/SiC. The analysis of the experiments conducted at ambient temperatures revealed that the friction coefficient increased with higher blade tip velocities (100~350 m/s). However, the coefficient was lower at high temperatures compared to room temperature. Furthermore, significant temperature increases were observed during rubbing at room temperature, whereas minimal temperature changes were detected on the rubbing surface at high temperatures.

Response to internal pressure shock and hoop strength of SiCf/SiC cladding

This study investigated the mechanical behavior of silicon carbide fiber-reinforced silicon carbide matrix (SiCf/SiC) cladding using expanding plug tests at 0.5 and 2 mm/min. A three-stage mechanical response for SiCf/SiC was observed, with significant differences in Stage 3 between specimens tested at different rates. Specimens tested at the slower rate (0.5 mm/min) exhibited a characteristic hoop strength of 112.4 MPa and homogeneous destruction behavior, indicative of uniform stress distribution. In contrast, the hoop stress in SiCf/SiC became unsteady at the faster rate (2 mm/min), leading to cracking at a lower nominal proportional limit stress (PLS), structural instability, non-uniform fiber pull-out, and a lower characteristic hoop strength of 92.4 MPa. This suggests that similar phenomena might occur at higher loading rates during internal pressure shock. Therefore, considering the application of SiCf/SiC, to conduct hoop strength testing at faster rates was recommend, such as 2 mm/min.

Vat photopolymerization of large-aperture high performance SiC mirror through multiphase carbon infiltration modification

Vat photopolymerization technique (VPP) shows advantages in rapidly preparation of complex structure silicon carbide matrix composites (Si/SiC). However, compared with traditional preparation technology, the properties of Si/SiC prepared via VPP are insufficient due to the presence of residual Si and carbon. Herein, the reaction mechanism of Si and carbon were systematically studied. Multiphase carbon was introduced into porous SiC preform via carbon precursor infiltration pyrolysis (CPIP) and graphitization methods. The content of residual Si was significantly decreased after reactive melt infiltration (RMI), and the residual carbon was eliminated through partial graphitization of the carbon. The influence mechanism of the carbon content and crystallinity on the reaction process of Si and carbon was studied. It suggested that the diameter of capillary channel and crystallinity of carbon are the main factors affecting residual carbon content in the final body after RMI. The sample with multiphase carbon achieved the best performance after RMI. The residual Si content, bulk density, flexural strength and elastic modulus are 11.58%, 3.04 g/cm3, 280.09 MPa and 355.48 GPa. In addition, the lowest coefficient of linear expansion was 2.39×10−6 K−1. Finally, a large-aperture SiC mirror with a diameter of 500 mm was prepared. Therefore, this research lays a foundation for promoting the application of large-aperture Si/SiC prepared via 3D printing.

Increasing the durability of an impregnated diamond core bit for drilling hard rocks

Wear rates of impregnated diamond core bits made from two composite diamond-containing materials (CDM) are studied by spark plasma sintering (SPS) in the temperature range 20–1350 ºC at a pressure of 30 MPa for 3 minutes while drilling granite. The addition of chromium diboride (CrB2) micropowder in an amount equal to 2% of the composition of CDM 25Cdiam–70.5WC–4.5Co leads to a twofold decrease in the wear rate. The wear resistance of crowns made from CDM 25Cdiam–70.5WC–4.5Co and 25Cdiam–68.62WC–4.38Co‒2CrB2 is maximized at a rotary speed of 250 rpm and an axial load of 900 kg, and minimized at 750 rpm and 1250 kg. The increase in wear resistance of the 25Cdiam–68.62WC–4.38Co‒2CrB2 crown is due to the refinement of the grains of the main wolfram carbide (WC) phase and the formation of strong adhesion of the diamond grains to the carbide matrix. Keywords: impregnated diamond core bit; composite; tungsten carbide; cobalt; chromium diboride; durability; spark plasma sintering.

Microstructure and Properties of TiN/TiCN/Al2O3/TiN Coating Enhanced by High-Current Pulsed Electron Beam

In this work, a TiN/TiCN/Al2O3/TiN coating deposited onto cemented carbide matrix by chemical vapor deposition was irradiated by high-current pulsed electron beam (HCPEB). The influence of pulse times on the phase composition, microstructure, and mechanical properties of the coating investigated. The results showed that no new phase was produced, the grain size of the coating surface was refined, the surface became flat, and the surface roughness decreased after HCPEB treatment. The TiN/TiCN/Al2O3/TiN coating presented a smooth surface with good mechanical performance after HCPEB. A maximum hardness was obtained after 15 pulses, and the 15-pulse irradiated coating showed better wear resistance. The improvement in the coating’s performance after irradiation was mainly attributed to the formation of grain refinement and crystal defects, as well as the change of stress field inside the coating. The objective of this study was to evaluate the potential of HCPEB modification in the preparation of high-performance coating by analyzing the microstructure and property of coating under different pulses.

Effect of Anisotropy of Reduced Graphene Oxide on Thermal and Electrical Properties in Silicon Carbide Matrix Composites.

Reduced graphene oxide, due to its structure, exhibits anisotropic properties, which are particularly evident in electrical and thermal conductivity. This study focuses on examining the influence of reduced graphene oxide in silicon carbide on these properties in directions perpendicular and parallel to the direction of the aligned rGO flakes in produced composites. Reduced graphene oxide is characterized by very high in-plane thermal and electrical conductivity. It was observed that the addition of rGO increases thermal conductivity from 64 W/mK (reference sample) up to 98 W/mK for a SiC-3 wt.% rGO composite in the direction parallel to the rGO flakes. In the perpendicular direction, the values were slightly lower, reaching up to 84 W/mK. The difference observed in electrical conductivity values is more significant and is 1-2 orders of magnitude higher for the flakes' alignment direction. The measured electrical conductivity increased from 1.2710-8 S/m for the reference SiC sinter up to 1.55 × 10-5 S/m and 1.2410-4 S/m for the composites with 3 wt.% rGO for the perpendicular and parallel directions, respectively. This represents an enhancement of four orders of magnitude, with a clearly visible influence of the anisotropy of the rGO. The composite's enhanced electrical and thermal conductivity make it particularly attractive for electronic devices and high-power applications.

Tribotechnical coatings

Wear and tear limits the possibilities and shortens the operational life of modern technical systems. Therefore, the importance and necessity of consideration of issues aimed at reducing frictional forces and increasing wear resistance cannot be doubted. The paper summarizes the theoretical and applied results of triboresistance studies of detonation coatings of the Nb-Zr-V-Si-C-MgC2 system under conditions of constant loading in the field of sliding velocities. It has been established that the ratio of the quality of the components that make up the surface modified structures changes. It is noted that at the initial test speeds the presence of lower metal carbides that are part of the coating dominates, with an increase in speed under the current load due to solid-phase and diffusion processes, higher ones are formed in the graphite matrix carbides with enhanced thermodynamic properties.