Increasing SiC Content Research Articles

Effect of SiC Contents on Wear Resistance Performance of Electro-Codeposited Ni-SiC Composite Coatings

This paper focuses on the wear resistance performance of Ni-SiC composite coatings with various contents of SiC particles. The coatings were characterized via a scanning electron microscope (SEM), X-ray diffractometer (XRD), and transmission electron microscopy (TEM), and the wear behaviors of different coatings were tested. The results show that SiC particle incorporation results in a nanocrystalline metal matrix and nanotwins in nickel nanograins. The microhardness and wear resistance Ni-SiC composite coatings increased with the increasing SiC content. Microhardness was improved due to the grain-refinement strengthening effect and the presence of a nanotwin structure. The dominant wear mechanism was described in two stages: the first stage involves the interaction of SiC particles/the counter ball, and the second stage involves the formation of the oxide film its breaking up into wear debris. A higher SiC content increased the duration of the first stage and slowed down the rate of breaking up into debris, thereby decreasing the wear rate.

Construction of gradient structure C/C–ZrC–SiC composites with good ablation resistance

With the upgrade of aircraft and the increasingly harsh service environment, it is urgent to develop high-performance thermal structural materials. In this study, inspired by foliar and root water uptake of trees, we propose a one-step facile method to achieve an autonomous gradient in C/C–ZrC–SiC sharp leading edge composites. The gradual increase of SiC content from top to bottom is beneficial to improve the heat transfer capacity of the composites. After oxyacetylene ablation for 60 s, the mass and linear ablation rates of the samples with gradient structure are 0.83 mg/s and 0.5 μm/s, 35 % and 83 % lower than conventional samples. The composites with gradient structure of ZrC and SiC are favorable to the formation of a compact and smooth ZrO2 oxide protective layer, which not only protects the composites from further penetration of O2, but also resists the mechanical denudation. The novel gradient structure composites with enhanced ablation resistance show a bright application prospect in next-generation thermal protection systems.

Enhanced fracture toughness of high entropy boride by adding SiC

The effect of SiC content (10 vol%, 20 vol% and 30 vol%) and sintering temperature (1800 °C, 1900 °C and 2000 °C) on the microstructure and mechanical properties of high entropy boride-silicon carbide (HEB-SiC) composites were systematically investigated in this work. The densification was gradually increased with the increase of SiC content and sintering temperature. More specially, the densification of HEB-30 vol% SiC composite obtained at 2000 °C was as high as 99.1 %. As for the mechanical properties, the dense HEB-30S-2000 composite possessed the highest fracture toughness (5.24 MPa m1/2) and Vickers hardness (28.5 GPa). The above significantly enhanced fracture toughness was closely pertained to the fracture modes adjusting. In details, after the addition of SiC, the branching and bridging of crack, the rupture of large SiC grain, and the deflection of crack existing near the HBE matrix and SiC particles jointly promote the improvement of fracture toughness. Besides, the Vickers hardness increased linearly with the relative density increasing. A simplified equation was established, which could effectually reflect the linear connection between the Vicker hardness and relative density (SiC content) of HEB-SiC composites. It will certainly play an important guiding role in the further development of HEB-SiC composites.

Influence of SiC particles on the microstructure and mechanical behaviors of AlMgScZr alloy processed by laser powder bed fusion

Laser powder bed fusion (LPBF) of AlMgScZr alloy has garnered significant attention as a high-strength aluminum alloy. However, its low modulus, Portevin-Le Chatelier (PLC) behavior, and weak strain hardening capability restrict its application in the aerospace sector. In this study, SiC/AlMgScZr composites with different SiC content have been successfully fabricated using LPBF. The inherent bimodal grain structure of AlMgScZr alloy was not completely altered by the addition of SiC particles. However, with increasing SiC content, heat accumulation increased, and the solidification cooling rate decreased. This led to an increase in the size of α-Al grains in the 5 wt% SiC/AlMgScZr composites. Meanwhile, movable dislocations can be efficiently preserved inside the grains, where they effectively accumulate and become entangled. Consequently, the strain hardening capability of the 5 wt% SiC/AlMgScZr composites improved by approximately 58 % compared to AlMgScZr alloy, with a strain hardening index (n) reaching 0.29. Additionally, the addition of SiC particles led to an increase in the elastic modulus (81.0 GPa). Furthermore, the reaction between Mg atoms and SiC particles resulted in the formation of Mg2Si, which altered the distribution of Mg elements and initiated the reactive precipitation of a Mg-rich phase. There is no competition between the diffusive migration of solute atoms and the motion of movable dislocations within the composites. The additional SiC particles effectively eliminated the PLC effect in the LPBF of AlMgScZr alloy. This work provides essential guidance for developing high-strength and high-stiffness aluminum matrix composites with excellent processing properties in LPBF technology.

Microstructure, phase evolution and mechanical properties of nickel-silicon carbide reinforced Ti6Al4V alloy processed by pulsed electric current sintering

In this work, fully densified Ni–SiC reinforced Ti6Al4V matrix composites were consolidated by pulsed electric current sintering (PECS) technique. The microstructural evolution and mechanical properties of the developed composites with varying SiC contents were investigated. The microstructural study revealed in-situ precipitation of TiC, Ti5Si3 and Ti3SiC2 strengthening phases within the composites. The α colony size in the composites was notably reduced compared to the fabricated SiC-deficient samples due to the addition of SiC additive into the Ti6Al4V alloy matrix. The in-situ precipitated phases enhanced the mechanical properties of the composites. Composite reinforced with 10 wt% SiC (TNi10SiC) displayed the highest hardness value of 609.8 ± 50.9 HV0.5 among the sintered samples, translating to an increment of about 88 % compared to the unreinforced sample T. Among the sintered samples, the highest flexural strength of 2094.32 ± 97.67 MPa was obtained for the TNi5SiC composite, after which the flexural strength deteriorates with increasing SiC content as witnessed in TNi10SiC composite with the least flexural strength of 863.67 ± 71.57 MPa due to agglomeration of the reinforcement phases within the composite. Samples reinforced with 0 wt% SiC experienced a ductile fracture, and the composites containing 2.5 wt% - 5 wt% SiC content witnessed intergranular and interlamellar fractures. However, at higher SiC content, reinforcement pull-out and debonding of the agglomerated reinforcement phases predominates, and composites fail by brittle fracture.

Microstructure and mechanical properties of high-pressure sintered B6O-SiC nanocomposites

Boron suboxide (B6O) is recognized as a superhard material with a low mass density, high resistance to chemical wear, and excellent wear resistance. Despite its desirable properties, the limited fracture toughness of B6O restricts its application in industrial contexts. This study presents the structural and mechanical characterization of B6O-SiC nanocomposites, which were synthesized via a high-pressure high-temperature sintering process of B6O powders and SiC whiskers. The sintering process induced fragmentation of SiC whiskers, resulting in the homogenous distribution of SiC fragments within the B6O matrix. An increase in SiC content was observed to decrease the composite's hardness, while initially reducing then enhancing its toughness. The nanocomposites containing 20 wt% and 30 wt% SiC whiskers exhibited significant improvements in fracture toughness, averaging 6.5 MPa m1/2 and 7.0 MPa m1/2, respectively—approximately threefold the toughness of polycrystalline B6O—while sustaining high hardness values of 36.3 GPa and 35.6 GPa on average. Microstructural analyses revealed that the composites’ superior mechanical performance is due to the presence of strong grain boundaries, as well as a high density of nanotwins and stacking faults. The findings demonstrate a viable method for producing B6O-based nanocomposites with enhanced hardness and toughness, potentially expanding their industrial applicability.

Effect of particle volume fraction on wear behavior in Al–SiC MMC coated on DIN AlZnMgCu1.5 alloy

Abstract In this study, DIN AlZnMgCu1.5 alloy surface (Al + SiC) was coated with metal matrix composite (MMC) by using hot press sintering method (HPSM). Al was used as matrix material and SiC powders were used as reinforcing material in the coating process on DIN AlZnMgCu1.5 alloy surface. Al/SiC MMC coating was produced at 600 °C under 120 MPa pressure and with varying SiC content (5, 10 and 15 vol.%). Optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used to examine the microstructure, elemental analysis and phase structure of both the coating zone and the transition zone between the substrate and the coating. The hardness was measured and a dry sliding linear reciprocating wear test was run to determine the mechanical properties of the coating layer. Consequently, the coefficient of friction (COF) and wear volume were determined. OM and SEM images showed a homogeneous distribution of SiC particles and a less porous structure. The hardness of the MMC coating increased with increasing SiC content. Also, the numerical analysis of the wear test simulation was done based on Archard’s law. The results of both wear tests showed that the volume loss values were consistent with each other and the amount of wear significantly reduced by increasing the rate of SiC reinforcement.

The effect of SiC on the growth habit of Fe-Ni-C system Ib gem grade diamond crystals

This article investigates the influence of different silicon carbide contents on the morphology and quality of diamond single crystals synthesized in the Fe-Ni-C-Si system under high temperature and pressure environments. It was found that silicon successfully entered the diamond lattice through bonding. As the doping concentration increases, the growth rate of diamond crystals decreases and defects appear on the crystal surface. The increase in internal stress in the lattice reduces the quality of diamond, as evidenced by the shift in Raman peak and half peak width of the diamond. Moreover, the infrared characterization results showed that the nitrogen element in the crystal exists as a single atom (C-center) in the diamond crystal, and the nitrogen content decreases with the increase of SiC content. This work provides insights for understanding the growth mechanism of natural diamonds and enriching the application of silicon doped diamond single crystals.

Incorporation of SiC on the mechanical properties, tribological performance, and oxidation resistance of HfC-SiC/a-C:H coatings prepared by hybrid HiPIMS and pulsed-DC magnetron co-sputtering

The multiphase nanocomposite HfC-SiC/a-C:H coatings consisting of HfC and SiC grains dispersed in the amorphous carbon matrix were deposited by hybrid HiPIMS and pulsed-DC magnetron co-sputtering. The incorporation of SiC ranging from 0 to 21.3 at.% on the chemical bonding state, nanocomposite structure, mechanical and tribological properties, and oxidation resistance of the coatings were explored. Results showed that the increase of SiC content is mainly at the expense of a-C:H matrix rather than nanocrystalline HfC, and is accompanied by changes in the HfC crystallinity. Nanohardness of up to 45 GPa was obtained for the HfC-SiC/a-C:H coating with 6.6 at.% SiC content. The optimum wear rate of 6.4×10−7mm3/N and friction coefficient of 0.2 were also obtained at 6.6 at.% SiC content. The oxidation resistance is enhanced with the increase of SiC content, which delays the oxidation temperature by 100 °C with respect to the HfC/a-C:H coating.

High-strength, high-toughness SiCp reinforced Mg matrix composites manufactured by semisolid injection molding

Particle-reinforced Mg matrix composites possess excellent mechanical and physical properties. In this study, a new processing technique, semisolid injection molding, was employed to fabricate SiCp/AZ91D composites. The microstructure and mechanical properties of the as-molded composites were investigated. The SiC particles were found to be uniformly distributed in the metal matrix and no agglomeration was observed. The presence of small voids next to the SiC particles was observed. The microhardness of the composites decreases with the increase of SiC content, and initially decreases and then increases to a stable level with the increase of casting temperature. The 2.5 wt% SiCp/AZ91D composite has the highest tensile strength, up to 10% higher than AZ91D and 18% higher than the 1 wt% SiCp/AZ91D composite. A large number of small dimples and spherical voids, formed after unmelted Mg particles were pulled out of the matrix, were observed on the tensile fracture surface. This study demonstrates that semisolid injection molding is a valuable technique for the manufacture of particle-reinforced metal matrix composites.

Directed energy deposition of SS 316L/SiC composites using coincident and coaxial wire-powder feeding

The wire-powder fed directed energy deposition (WP-DED) process enables the fabrication of metal matrix composites (MMCs) with a high deposition efficiency. Lateral wire-powder feeding as well as lateral wire and coaxial powder feeding are two existing methods for WP-DED of MMCs. However, the lateral filler injection limits the fabrication of three-dimensional parts with complex geometry. In this study, we applied the coaxial wire-powder fed DED (CWP-DED) to fabricate the SS 316L/SiC parts with different SiC weight fractions. The effects of SiC content on defects and microstructure of as-built parts were investigated. Three types of interior defects including pores, inclusions, and cracks were observed in as-built samples fabricated with high SiC content. With an increase in SiC content, the grains were refined by dissolved nano-scale SiC particles and more γ-(FeCrNi) phases transformed into α-(FeCrNi) phases. Tensile properties and the underlying strengthening mechanisms of as-built SS 316/SiC specimens were elucidated. This paper will guide the process development for CWP-DED of high-performance MMCs.

Analysis of oxidation behavior of laser cladding SiC-Ti based composite strengthening coating

In this paper, the oxidation behavior and high-temperature tribological properties of laser cladding Ti-Al-Si-SiCx system coatings at 800°C in the air were studied. The results demonstrated that these coatings had Ti5Si3/Ti3Al eutectic structure before oxidation. The results of oxidation resistance suggested that the oxidation weight gain conformed to the parabolic law. An appropriate increase in SiC content is beneficial to lower the oxidation rate. The Ti5Si3 phase has excellent oxidation resistance. TiC phase forms CO2 product during the oxidation process. In addition, the diffusion rates of Ti and Al elements in the oxide layer are different. The combined effect of the two eventually leads to the gradual formation of pores in the oxide layer. The TiC-reinforced phase improves the friction coefficient of high-temperature friction, but its introduction significantly improves the high-temperature wear resistance. Additionally, the adhesion of the oxide film in the high-temperature wear process exerted a great influence on the wear mechanism. Ti-Al-Si-SiC3 exhibited the lowest wear rate of 6.73 × 10−7 mm3 N−1 m−1. The wear mechanism is primarily adhesive wear, abrasive wear, and oxidative wear.

On the microstructural and mechanical responses of dual-matrix Al-Ni/SiC composites manufactured using accumulative roll bonding

This article discusses the correlation between the microstructural and mechanical changes in the dual-matrix Al-Ni/SiC composites processed by Accumulative Roll Bonding (ARB) technique. Three different SiC concentrations, 1, 3, and 5% were considered to reinforce Al and Al-Ni dual-matrix composites. ARB process was applied up to 7 cycles to manufacture a composite with homogenous dispersion of the three phases. The results showed that the presence of Ni layer between Al and SiC particles enhanced the dispersion of SiC in the matrix, which positively affect the mechanical strength. The maximum tensile achieved was 257 MPa for composite containing 3 % SiC after 7 ARB cycles compared to 37.2 MPa for the AA1050. Increasing SiC content reduces the adhesion between Al and Ni layers, which reduces the elasticity of the composites. However, for the composites with 5% SiC, after 3 ARB cycles, the strength was reduced due to the cracking of the Ni layer caused by the stress concentration around the SiC particles. The hardness values of the ARBed AA1050, AA1050-Ni, and AA1050-Ni/5 wt% SiC are 85.5, 93.5, and 109.7, respectively, after 7 ARB cycles. In terms of strength, the samples with 3% SiC content showed the optimum stress enhancement with minimum reduction in the elongation, which achieve a compromised response for many applications.

Understanding the effect of SiC/epoxy coating on surface flashover under DC voltage: from surface charge accumulation

Charge accumulation at the insulator surface significantly alters the electric field distribution under DC voltage and can lead to unpredictable flashover. It is realized that the surface flashover voltage is reliant on the charge distribution approaching flashover occurrence (CDAFO). A method of how to judge the moment approaching flashover was proposed in this study to clarify how surface charges induced flashover, whereby the dynamic distributions of surface charges, including the CDAFO, were obtained from the instant of voltage application to the moment approaching flashover. The resulting flashover was analyzed with regards to insulators coated in SiC/epoxy, including an examination of the dominant charging pathway during voltage rising and a discussion of the relationship between the CDAFO and flashover voltage. Despite voltage polarities and SiC content, a reversal of charge polarity from hetero-polar to homo-polar was observed during voltage rising. Furthermore, it was discovered that the CDAFO was homo-charge accumulation, and an increase in SiC content resulted in greater homo-charges. A theory outlining homo-charge’s enhancement of flashover voltage by weakening the electric field near the high voltage electrode was also proposed. Consequently, because of the improved effect of homo-charges on flashover voltage, the addition of SiC led to the boost of flashover voltage.

Influence of characteristic parameters of SiC reinforcements on mechanical properties of AlSi10Mg matrix composites by powder metallurgy

The bottleneck problems of SiC particles reinforced AlSi10Mg composites (SiC/AlSi10Mg) prepared by traditional casting method, such as composition segregation, interface reaction and coarse microstructure, can be effectively improved by powder metallurgy with lower processing temperature. In this study, the influence of SiC particle size and content on the properties of SiC/AlSi10Mg was systematically analyzed. SiC/AlSi10Mg composites were prepared by planetary ball milling, spark plasma sintering (SPS) and hot extrusion composite preparation process. The obtained composites presents dense microstructure without the formation of interfacial reaction phase. The distribution of micron SiC particles (μm-SiC) in the matrix is relatively uniform, and nano SiC particles (nm-SiC) slightly agglomerates with the increase of the content. The strength of SiC/AlSi10Mg increases with the increase of nm-SiC content, which is mainly attributed to dispersion strengthening, dislocation strengthening and grain refinement strengthening. The strength of SiC/AlSi10Mg hardly changes with the increase of μm-SiC content, but the elongation decreases gradually. The deformation between μm-SiC and AlSi10Mg matrix is not coordinated and μm-SiC cleave the AlSi10Mg matrix. The irregular boundaries of μm-SiC are easy to produce stress concentration during loading, leading to interface cracking or μm-SiC fracture. Therefore, μm-SiC are difficult to play a significant strengthening effect to composites. With the increase of SiC content, the fracture mechanism of composites gradually changes from ductile fracture to brittle fracture in SiC agglomeration region. This study lays a theoretical and experimental foundation for the controllable preparation and performance optimization of high strength and toughness AMCs reinforced by SiC particles.

Microstructure and mechanical properties of SiC-reinforced Inconel 718 composites fabricated by laser cladding

Laser cladding provides the feasibility for fabricating various ceramic-reinforced metal-matrix composite coatings, where the reinforcement content plays a critical role in influencing the residual stresses and the performance of the cladded layer. In this paper, the SiC-reinforced Inconel 718 composites are prepared by LC, and the microstructure and mechanical properties (stress distribution, microhardness, wear behavior) of the cladded layers with different SiC contents are investigated. Based on multi-physics modeling complemented by experimental validation, the thermal stress distribution is analyzed and the residual stresses of the formed Inconel 718/SiC are investigated. The addition of an appropriate amount of SiC can help to relieve residual stresses in the clad layer, with the layer containing 5 wt% SiC corresponding to the minimum residual stress. Moreover, the addition of ceramic particles is conduced to refine the microstructures, and metallic carbides generated by the decomposition of SiC in combination with the diffused elements of the matrix play a positive role in the hardness improvement. The wear resistance of the coatings also increases significantly with increase of SiC content, and the wear mechanism is dominated by abrasive wear, accompanied by oxidation wear, fatigue wear and adhesive wear.

Effect of SiC content on microstructural evolution and tribology properties of laser-clad TiC-reinforced Ti-Al-Si composite coatings

This work prepared (Ti-Al-Si)-X (x = 1, 2, 3, 4) coatings on TC4 alloy matrix composites by laser cladding to improve their surface mechanical properties. Meanwhile, the effect of the content of SiC added to the Ti-Al-Si system on the properties and microstructures of the original coatings was explored. The results showed that the reinforced composite coatings contained matrix phases (TiAl, Ti3Al, TiAl3) and reinforcing phases (Ti5Si3 and TiC). As SiC content increased, the matrix phases formed in the coatings showed different results on the Ti-Al-Si ternary phase diagram due to the introduction of C, a stabilizer of ɑ-Ti alloy. Meanwhile, TEM results indicated the existence of Ti5Si3 phase and Ti3Al secondary phase in the Ti-Al-Si-3 layer. Compared with the TC4 matrix, the reinforced composite coatings had higher microhardness with average values of 780.9 HV0.3, 853.9 HV0.3, 985.0 HV0.3 and 943.5 HV0.3 for the four coatings, respectively. The wear resistance of the reinforced composite coatings increased first and then decreased with increasing SiC content, which was the result of the matrix phase transformation. The Ti-Al-Si-3 coating had the highest microhardness (1092HV0.3) and wear resistance (the friction coefficient, the wear scar width and wear weight loss were 0.37, ∼0.83 mm and 1.8 mg, respectively). The above analysis and results demonstrated that the Ti-Al-Si-3 layer had superior mechanical properties compared with those of other reinforced coatings.

Microstructure and mechanical properties of carbon-precursor-added B4C and B4C−SiC ceramics subjected to pressureless sintering

Organic-carbon-precursor-added B4C and B4C–SiC ceramics were subjected to pressureless sintering at various temperatures. The carbon precursor increased the densification of the B4C and B4C–SiC ceramics sintered at 2200 °C to 95.6 % and 99.1 % theoretical density (T.D.), respectively. The pyrolytic carbon content of the B4C–SiC composite decreased with increasing SiC content. The graphitization degree of pyrolytic carbon decreased slightly with the amount of carbon precursor and content of SiC. The 95 wt. % B4C–5 wt. % SiC composite added with 7.5 wt. % carbon precursor and sintered at 2200 °C outperformed the other B4C–SiC composites, and its sintered density, flexural strength, Young’s modulus, and microhardness were 98.6 % T.D., 879 MPa, 415 GPa, and 28.5 GPa, respectively. These values were higher than those of composites prepared via pressureless sintering and comparable to those of composites fabricated via hot pressing and/or using metal or oxide additives.

Improving the Ablation Properties of Liquid Silicone Rubber Composites by Incorporating Hexaphenoxycyclotriphosphonitrile.

The ablative properties of epoxy-modified vinyl silicone rubber (EMVSR) composites containing hexaphenoxycyclotriphosphonitrile (HPCTP) have been systematically studied. The strength of the ablation char layer was greatly enhanced with the addition of HPCTP, which induced the formation of a more complete, denser, and thicker char during oxyacetylene ablation tests. Moreover, the HPCTP-containing EMVSR composites demonstrated lower thermal conductivity and pyrolysis rate when compared with those without HPTCP. At the same time, the thermal insulation properties of HPCTP-filled composites were improved under low heat flow ablation scenarios. The reduction of graphitic carbon content, the formation of phosphate-like crystals as well as the increase of SiC content contributed to strengthening the char layer, which was critical for improving the ablation properties. The optimum char layer strength and thermal insulation properties were achieved when the content of HPCTP was 15 phr, whereas an optimum ablation resistance was achieved at 25 phr HPCTP. This suggests that HPCTP-modified EMVSR composites can be used for thermal protection purposes, especially in the fields of aerospace and aeronautics.

Plasma sprayed TiC–Ti5Si3–Ti3SiC2–SiC composite coatings using annealed Ti–SiC composite powders based on SiC content

The TiC–Ti5Si3–Ti3SiC2–SiC ceramic composite coatings were prepared with in-situ reaction by plasma spraying annealed Ti–SiC–C composite powders. The effect of SiC content in the annealed composite powders at 1200 °C on the microstructure and properties of the coatings was studied. With the increase of SiC content, the phases in the annealed Ti–SiC composite powders changed from Ti, SiC, TiC and Ti5Si3 to SiC, TiC, Ti5Si3 and Ti3SiC2. The phases of the sprayed coatings were mainly composed of TiC, Ti5Si3, Ti3SiC2 and a small amount of residual Si, and their content were closely related to SiC. The coating hardness first increased and then decreased, while their mass loss showed an opposite trend to that of hardness. The T1SCC (molar ratio of Ti-SiC-C is 3:1:1) coating had the highest hardness of HV 1509 and the lowest mass loss of 0.0019 g, whereas its fracture toughness was 3.51 MPa m−2.