Carbide Particle Size Research Articles

Effect of cooling temperature on microstructure and mechanical properties of Nb microalloyed hot-rolled rebar

In this study, the Gleeble-3800 thermal simulation tester was used to simulate various cooling temperature processes for two groups of rebar. Then, the microstructure, precipitation, and mechanical properties of the rebars were characterized using SEM (scanning electron microscopy), EBSD (electron backscatter diffraction), HRTEM (high resolution transmission electron microscopy), and MST810 (universal tensile testing machine). The effect of cooling temperature on the microstructure and mechanical properties was systematically investigated. The results showed that reducing the cooling temperature from 750 °C to 600 °C decreased the ferrite grain size in 0.032 wt % Nb rebar to 7.03 ± 1.5 μm, compared to the 0 wt% Nb rebar. In addition, the pearlite lamellar spacing was refined to 0.103 ± 0.5 μm, and the average particle size of elliptical Nb-rich composite carbides was 9 nm. The tensile strength and yield strength reached 795 ± 9 MPa and 638 ± 8 MPa, respectively, with an elongation after fracture of 17.78 ± 1.0 %. The fracture surface exhibited a dimple morphology.

Effect of sintering temperature, additive ratios, and reinforcement of boron and boron carbide particle sizes on the mechanical and tribological properties of the synthesized Cu-Cr hybrid composites

In this study, hybrid composites were generated by combining Copper (Cu) powder with Chromium (Cr) powder at a fixed weight of 1 %, as well as Boron (B) and Boron carbide (B4C) powders at specific weight ratios (1 %, 2 %, 3 %, and 4 %), with variable particle sizes (1 µm and 44 µm). Powder metallurgy production parameters were employed to produce two sets of samples at sintering temperatures of 750 °C and 850 °C. Analysis of the microstructure of the samples was performed, as well as hardness and abrasion tests. A variety of B/B4C ratios and particle diameters were employed to characterize Cu-based hybrid composites using SEM-EDS and XRD. Weight loss graphs and coefficient of friction values were generated for each sample subsequent to wear tests. The results of the tests indicated a 76.25 % increase in hardness values with B reinforcement and a 60.71 % increase with B4C reinforcement in comparison to a pure Cu sample. As the sintering temperature increased and the size of the reinforcement particles decreased, the hardness of the material increased, resulting in identical results in the wear testing. A tribo-layer was observed to have formed between the wear pin and the samples in the new hybrid composites with Boron matrix in the SEM images taken after wear. The wear resistance properties of Cu matrix hybrid composites were found to be enhanced by this tribolayer.

Vat photopolymerization of silicon carbide strengthened alumina ceramic composites with honeycomb structure for heat insulation and oil/water separation

In this study, the effects of different silicon carbide (SiC) particle sizes on the viscosity and curing behavior of alumina (Al2O3) ceramic suspensions were thoroughly investigated. The findings revealed that increasing the size of SiC particles led to a noticeable decrease in the viscosity of the suspension. The Al2O3 ceramic suspension with 0.6 μm SiC powder demonstrated a shallower cure depth and wider excess width compared to the suspension with 1.0 μm SiC powder. Sintering tests demonstrated that the properties of the SiC–Al2O3 ceramics improved at higher sintering temperatures. Moreover, a high-performance honeycomb ceramic was successfully designed and fabricated with a porosity and compressive strength of 30.8 % and 188 MPa, respectively. Finally, the SiC–Al2O3 honeycomb ceramics were effectively applied in heat insulation and oil-water separation applications, demonstrating their remarkable capabilities.

Effect of C content on the microstructure and properties of in-situ synthesized TiC particles reinforced Ti composites

Titanium matrix composites (TMCs) have garnered substantial attention from researchers owing to their outstanding properties. Nonetheless, the strength and ductility of TMCs hardly co-exist and often show a trade-off between each other. In this study, we employ an ultra-thin graphite powder sheet as the carbon source and employ Ti/C composites with varying carbon contents, prepared via a layer-stacked laminated sintering method, to ensure a comprehensive in-situ reaction and uniform reinforcement distribution. With increasing carbon content, noticeable alterations occur in the size, concentration, and morphology of the titanium carbide (TiC) particles. The increase of TiC particle content is found to boost the ultimate tensile strength of the composite. However, this improvement comes at the expense of reduced elongation. Notably, as the carbon content reaches 1.81 wt%, the yield strength and ultimate tensile strength of the composites soar to 354.4 MPa and 575.4 MPa, respectively. These values represent a remarkable increase of 75.4% and 65.0% compared to pure titanium, while maintaining an acceptable elongation of 6.45%. This study unveils a promising approach for significantly enhancing the mechanical properties of titanium alloys.

Microstructure and properties of Fe-VC pulsed plasma arc cladding layers under different cooling conditions

The impact of pulse frequencies on the microstructure and properties of the Fe-VC composite plasma arc cladding layer, utilizing different cooling methods were investigated. The pulse frequency was found to be a crucial factor, varied pulse frequencies, ranging from 0.5 Hz to 500 Hz, resulted in significant changes in carbide particle size, matrix grain size, microhardness, and corrosion resistance. Notably, when the pulse frequency was set at 500 Hz with water cooling, the Fe-based matrix grains and carbides in the cladding layer achieved their smallest sizes, measuring 0.96 μm and 77 nm, respectively. Furthermore, the cladding layer exhibited outstanding comprehensive performance, boasting a microhardness of 1130 HV0.2 and corrosion resistance approximately 25 times higher than that of the low carbon steel.

New insight into the relationship between the C-Cr ratio and carbides, mechanical property of cold working die steel

An new insight into the relationship between the C-Cr Ratio and carbides, mechanical property Cr Alloyed of cold working die Steel were investigated by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), rockwell hardness and impact toughness tests. The ‘C-Cr ratio’ and ‘Cr equivalent E Cr ‘ parameters were introduced to characterize the carbide characteristics and mechanical properties. The results show that the precipitation temperature of M7C3 eutectic carbides grows linearly with E Cr when the E Cr value is less than about 22, and the precipitation temperature increases significantly when the E Cr value exceeds 22, and the growth curve takes a plateau turn. The precipitation temperature of MC carbides decreases approximately linearly with E Cr value, and the precipitation of MC eutectic carbides will be completely suppressed when the E Cr value exceeds 19. The content of eutectic carbides in the as-cast organization is more, the shape is more complex and the size is larger. The ratio of Cr and Fe content in the composition of M7C3 eutectic carbides is linearly related to the Cr-C ratio; the content of carbides in the steel after forging and the E Cr value are basically linear. The average particle size and the average length of longitudinal carbides after forging are basically proportional to the E Cr value. The average particle size of longitudinal carbides after forging is greater than 4 μm and the E Cr value are basically linear; when the Cr content is greater than 4%, the quenching peak hardness of steel and the C/Cr have a good linear relationship; as the E Cr value gradually increases, the impact toughness of steel gradually decreases. These results are important not only for understanding the strengthening mechanisms of die steel, but also for the composition design and carbide control of cold working die steel.

Predicting crystallite size of Mg-Ti-SiC nanocomposites using an adaptive neuro-fuzzy inference system model modified by termite life cycle optimizer

In this study, Mg-Ti-SiC composite powders with varied micron and nano silicon carbide (SiC) particle sizes were fabricated utilizing the ball milling technology at various milling times. The effect of reinforcement particles sizes and milling time on the morphology and microstructure of the magnesium composite powders was characterized. Then, we developed a machine-learning model based on Adaptive Neuro-fuzzy Inference System (ANFIS) modified with termite life cycle optimizer to predict the crystallite size of the produced composites. The average particles size in all composites including micron SiC (µSiC) and nano SiC (nSiC) always decreased with increasing milling time and SiC content, and the most optimal reduction in particle size was achieved after 16 h of milling for both configurations, which were 5.12 µm and 1.96 µm, respectively. Changing reinforcement particle size from micron to nano caused the peak intensities of Mg and Ti more decreased and phases Ti5Si3 and TiC were observed after milling for 16 h in ND composite powder. With increasing milling time in Mg-25 wt% Ti-5 wt% µSiC, the crystallite size decreased from 31 nm to 13.62 nm after 1 h and 32 h milled, respectively. The most optimum reduction in crystallite size occurred in the composite powders including nSiC, in which crystallite size decreased to 13.35 nm. The developed Machine learning model was able to predict the evolution of the crystallite size of the produce d composites with very good accuracy.

Precipitation mechanism of dispersed carbide in a gear carburizing layer and its effect on properties

AbstractHeat treatment is carried out on 20MnCr5 gear steel using a cycle carburizing process. The dispersed carbide precipitation mechanism in the carburized layer of 20MnCr5 gear steel is revealed, and the metallographic organization, microhardness, wear resistance, and fatigue properties are tested. The precipitation mechanism of two kinds of dispersed carbides at grain boundary and inside grain in carburized layer of gear steel was observed by experiment. The size of dispersed carbide particles is 0–5 μm, and 90% of the dispersed carbide is appropriately smaller than 1 μm. Compared to gears without dispersed carbide, gears with dispersed carbide have high microhardness within a 0.4 mm depth below the surface and a low friction coefficient. It has been verified by bench test that the presence of diffuse carbides dramatically improves the fatigue life of the gears after shot blasting and shot peening.

FABRICATION OF A NOVEL FeB-B4C COMPOSITE POWDER AND EVALUATING ITS POTENTIAL FOR ENERGY STORAGE APPLICATIONS

The development of energy storage devices is critical for humanity to declare its independence from fossil fuels. Supercapacitors and batteries are rapidly growing technologies. Nevertheless, their current progress is still insufficient to meet global demand. Therefore, advances in new generation and tailored materials for energy storage applications are urgently needed. Herein, for the first time, a novel composite of FeB-B4C powder was synthesized by a one-pot sol-gel technique, and its potential as an active material for electrodes in energy storage devices was investigated. The phase analysis showed that a composite powder containing 91±5% B4C and 9±5% FeB was obtained without unwanted excess phases such as graphite, boron, or iron oxide. Scanning electron microscopy images of the composite powder revealed the formation of elongated boron carbide particles connected with spherical iron boride ones. The size of the boron carbide particles was found to be in the range of 1 to 10 µm, while the iron boride particles were formed in the submicron range. The synthesized composite's electrochemical properties were investigated using a three-electrode set-up. Cyclic voltammetry (CV) and galvanostatic charge/discharge tests (GCD) were employed. The results obtained indicate the pseudocapacitive behavior of the electrodes with a specific capacitance of 8.28 F/g.

Mechanical characteristics and deformation behavior of Al polycrystal reinforced with SiC particles

Molecular dynamics models are established to investigate the influence of silicon carbide (SiC) particle size and strain rate on the mechanical characteristics and deformation behavior of aluminum (Al)/SiC composite. The results show that the ultimate strength of the Al/SiC composite increases from 0.788 to 0.910 GPa as the SiC reinforcement particle size increases from 10 to 30 Å, due to load transfer effects and barriers to dislocation motion. Plastic deformation of Al/SiC composite decreases with increasing SiC particle size, manifested by a lower proportion of atoms subjected to high shear strain for larger SiC particles. The SiC particle size also influences the change in crystal structure during deformation, as shown by the larger particles better supporting the Al matrix in minimizing the dislocation movement. The study shows that the grain boundary and Al/SiC interface play a significant role in the mechanical properties of the composite by impeding the evolution of dislocation and stacking fault. Moreover, the higher strain rates lead to increased ultimate strength and flow stress due to a greater rate of deformation and energy storage. The distribution of shear strain in the composite shows concentrated deformation at the grain boundary, and the large shear-strain region decreases as the strain rate increases. Additionally, higher strain rate leads to more formation of hexagonal-close-packed and amorphous structures, increased dislocation density, and material failure.

Modulating the microstructure and mechanical properties of β-Ti-reinforced bulk metallic glass composites by carbon addition

The effects of carbon addition on the microstructure modifications and mechanical response of Ti48Zr20Nb12Cu5Be15 BMGCs are investigated. With increasing carbon content from 0.1 at.% to 0.3 at.%, the evolution of morphology and solid solution strength is not obvious, and the ductile-brittle transition is presented due to the large changes of the sub-Tg relaxation enthalpies, ΔHrel, in the glass matrix when the interstitial C content increasing to 0.5 at. %. Once the C content excess this threshold value, a large melting area and open cracks are mainly related with the size and number of carbide particles and the magnitudes of free volume in the glass matrix, which indicates the appearance of large-sized vermicular-like structure is the cause of instability of composite material. In addition, when C exceeds its limit solute concentration, harder β-Ti-reinforced dendrites and precipitate phases can suppress the initiation of shear bands, and the transfer ability of the concentrated stress to the surrounding glass becomes weaker, which promotes the formation of cracks, resulting in brittle failure.

Evolution of the microstructure and mechanical properties of Sanicro 25 austenitic stainless steel after long-term ageing

A newly developed heat-resistant austenitic steel, Sanicro 25 is currently considered the leading candidate material for an advanced ultra-supercritical installation. The test material was subjected to long-term ageing (up to 30,000 h) at 700 and 750 °C, after which investigations into the microstructure, identification of precipitates, and testing of mechanical properties were conducted. Sanicro 25 had an austenitic microstructure with annealed twins and numerous large primary NbX and Z-phase precipitates in the as-received condition. It was found that the long-term ageing of the steel resulted in numerous precipitation processes. For example, M23C6 carbides, Laves, σ and G phases occurred at the grain boundaries. However, Z-phase precipitates, ε_Cu particles, and Laves phase were observed inside the grains. At the same time, compound complexes of precipitates based on the primary Z-phase precipitates were revealed in the microstructure. The ageing process increased the particle size of M23C6 carbides and the σ phase. After longer ageing times, a precipitate-free zone (PFZ) near the grain boundaries was observed. The precipitation processes initially lead to an increase in the strength properties of the steel. However, after 5000 h, an over-ageing effect was observed at 750 °C, which was not observed at 700 °C.

Effect of Refined Spheroidizated Structure on Mechanical Properties of Spring Steel 51CrV4

The steel 51CrV4 is widely used for production of springs. Materials research into spring steels aims to meet the requirements of industry, which mainly concern high yield and tensile strengths. Ductility has to be retained as the strength is increased. Also, the resistance against brittle fracture is im-portant, measured as fracture toughness. Enhancement of the mentioned mechanical properties can be accomplished by structural refinement. One possible way to refine the final quenched and tem-pered structure is to refine the soft annealed structure before quenching. The article is devoted to the Accelerated Carbide Spheroidisation and Refinement (ASR) with a comparison to conventional soft annealing (SA) in the 51CrV4 spring steel. Both spheroidization treatment (ASR by induction heating, SA by electric furnace) led in different carbide particle sizes. The carbide refinement alters the mate-rial’s behaviour during quenching. Finer carbides dissolve more rapidly during austenitization at the quenching temperature. It is possible to lower the quenching temperature thanks to carbide refine-ment. Mechanical properties after hardening with different quenching temperatures were positively affected too.

EFFECT OF TANTALUM ON THE IMPACT RESISTANCE OF 12% CR STEELS SUBJECTED TO THERMOMECHANICAL TREATMENT

The effect of tantalum on the impact resistance of 12% Cr steels with different tantalum content (12CrTaNb and 12CrNb) was investigated in impact tests in the temperature range from -40 to +120°C with determining the brittle-ductile transition temperature as the temperature in the middle between the upper and lower shelf energies. Both 12% Cr steels were thermomechanically treated by alternating 1050°C annealing and forging in addition to standard normalizing treatment with high-temperature tempering. It was found that for Ta-alloyed 12% Cr steel, the entire fracture toughness versus temperature curve is 30-50 J/cm2 higher over the entire temperature range, including the upper and lower shelf energies, and the brittle-ductile transition temperature is 10°С lower. The main structural parameters of Ta-alloyed 12% Cr steel which can have a beneficial effect on toughness are a smaller initial austenite grain size, a larger average size but lower density of M23C6 carbide particles along low-angle martensite lath boundaries, and a larger volume fraction of VX carbonitrides.

Effect of post-heat treatment on microstructure and mechanical properties of nickel-based superalloy fabricated by ultrasonic-assisted wire arc additive manufacturing

Ultrasound as a novel auxiliary means has been gradually used in additive manufacturing (AM) process. Ultrasonic cavitation and acoustic streaming can effectively control the columnar to equiaxed transition of grain structures, which can improve the anisotropy of mechanical properties. In addition, post-heat treatment (PHT) was considered to improve the microstructure uniformity and mechanical properties of alloys prepared by AM. In this study, we investigated the effect of PHT on the microstructure and mechanical properties of IN625 superalloy fabricated by ultrasonic-assisted wire arc additive manufacturing (UA-WAAM). The results showed that ultrasonic successfully inhibited the growth of columnar grains, and the microstructure was replaced by equiaxed grain structure. When the PHT temperature reached 1200 °C, the grain morphology changed, and a large number of annealing twins were generated in the alloy. Further, with the increase of PHT temperature, Laves phase disappeared and carbide particle size decreased. The results of mechanical properties showed that the microhardness and yield strength of the IN625 superalloy decreased with increasing PHT temperature, but the elongation and strain hardening ability increased significantly. The combination of UA and PHT provided an opportunity to achieve excellent strength-ductility balance in metals and alloys fabricated by AM.

A Novel Technique for the Preparation of Iron Carbide and Carbon Concentrate from Blast Furnace Dust.

Blast furnace (BF) dust is a typical refractory iron resource. A novel technology-based utilization of BF dust as iron carbide and carbon concentrate by applying carburization roasting followed by magnetic separation and acid leaching is proposed. Under optimized conditions, an electric arc furnace (EAF) burden assaying 80.79% Fe and 7.63% C with a corresponding iron recovery rate of 87.26% and a carbon concentrate assaying 67.06% C with a corresponding carbon recovery rate of 81.23% were prepared. Furthermore, the carburization behavior and separation mechanism were revealed using X-ray powder diffraction, scanning electron microscopy, and optical microscopy. The results show that the separation efficiency of iron carbide, gangue, and carbon is very low. Na2SO4 is a highly effective additive to strengthen the separation efficiency as it can enhance the carburization index, enlarge the iron carbide particle size, improve the embed embedded relationship of iron carbide and gangue, and promote the gangue leaching efficiency. The study demonstrates that preparation of iron carbide and carbon concentrate from BF dust using the proposed technology is a feasible method.

Comparative Study into Microstructural and Mechanical Characterization of HVOF-WC-Based Coatings

The main objective of this work was to characterize and compare the microstructural and mechanical properties as well as erosion resistance of WC-12Co and WC-10Co-4Cr coatings. The High Velocity Oxy Fuel (HVOF) process was applied to carbon manganese steel API 2H typically used in oil and gas industries. Microstructural characterization of feedstock powder and coatings was conducted using scanning electron microscope (SEM), energy dispersive X-ray spectroscopic (EDS) analysis, X-ray diffraction (XRD) for phase determination, powder particle size distribution, and surface roughness measurement. The average particle size of the former powder was 13.7 µm whereas it was 28.1 µm for the latter. The results showed that the smaller particle size tends to melt easier than the larger one, as deduced from SEM images and surface roughness measurements. EDS and XRD results of both coatings indicated the occurrence of WC decomposition where the powder particle size plays a significant role in these results. Mechanical characterization was discussed through comparing hardness, erosion, and adhesion test results of both coatings. WC-10Co-4Cr coating exhibited higher hardness than WC-12Co as well as higher erosion resistance, due to the extent of decomposition of WC and also to carbide particle size within the coating layer; these are the same reasons for the superior adhesion strength of the former coating compared to the latter one as per ASTM Standard “C633- 13”.

Facile Electrochemical Preparation of Nano-sized Ultra-high-temperature Ta1−xHfxC Ceramic Powders

Nano-sized powders of the Ta1−xHfxC class of ceramics, with compositions of Ta0.2Hf0.8C, Ta0.5Hf0.5C and Ta0.8Hf0.2C, were successfully synthesized from mixtures of the corresponding metal oxides and graphite by electro-deoxidation in molten CaCl2 at 1173 K. X-ray diffraction revealed that the as-prepared Ta0.8Hf0.2C mixed carbide had a single-phase cubic structure whereas Ta0.5Hf0.5C and Ta0.2Hf0.8C had dual-phase cubic structures, indicating that the large proportion of Ta promoted the formation of a homogeneous solid solution of TaC and HfC during synthesis. Electron microscopy proved that the particle size of the mixed carbides was in the nano range, while energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirmed that the intended compositions had been attained. Notably, the electrochemical method of synthesizing Ta1−xHfxC mixed carbides proceeds at a significantly lower temperature than the conventional preparation methods. This offers a number of key advantages in that it saves energy, gives better control over composition and allows for higher purity, and it suppresses in situ sintering and thus enables the formation of nanoparticles.

Influence of the Silicon Carbide Particle Size on Dielectric Characteristics, Thermal Conductivity, and Microwave Absorption of Pressureless-Sintered AlN–(20–50)% SiC Composites

Influence of the Silicon Carbide Particle Size on Dielectric Characteristics, Thermal Conductivity, and Microwave Absorption of Pressureless-Sintered AlN–(20–50)% SiC Composites

RELATION OF KINEMATICS AND CONTACT FORCES IN THREE-BODY SYSTEMS WITH A LIMITED NUMBER OF PARTICLES

In many tribological systems, an intermediate layer of a limited number of abrasive particles exist. Thereby, the resulting wear and friction phenomena are desirable in many manufacturing processes, such as lapping or polishing, whereas in machine elements, they are unwanted due to reducing lifetime or performance.For a better understanding of the contact phenomena and the interaction of tribological systems with an intermediate layer of a limited number of particles, fundamental investigations are carried out on a tribometer test rig. For this purpose, two test scenarios are investigated, a) the kinematics and contact forces of single geometrically defined particles such as dodecahedron, icosahedron and hexahedron, and b) the contact forces and surface roughness of a layer of silicon carbide particles of different sizes.The measured ratio of tangential to normal force can be used as an indicator of the dominating kinematics of the particles and of the generated surface roughness, respectively. The higher the force ratio, the higher the tendency to slide for a given particle type and paring of particle and counter body.For one geometrically defined particle the short-time Fourier transform additionally helps to distinguish the state of motion since the excited frequencies during rolling are reduced. For a layer of silicon carbide particles, the velocity and particle size have the strongest influence on the overall motion and the surface roughness produced. Larger particles tend to slide and create more scratches, while smaller particles tend to roll and create indentations in the counter body. Furthermore, for the same particle size, an increase in velocity causes a transition from sliding to rolling, resulting in an increased surface roughness.