Increasing Sintering Temperature Research Articles

Use of Ultrasound to Identify Microstructure-Property Relationships in (AlN + WC) Fabricated with Electroless Ni Producing

In order to improve the properties of the materials produced by the powder metallurgy method, first of all, powders (16.59% AlN + 6.63% WC) were coated with nickel (Ni) by electroless method, and then box boriding, which is one of the most widely used surface coating methods, was applied. A composite formed with (16.59% AlN + 6.63% WC)76.7Ni was prepared under the Ar shroud in the temperature range of 1000-1400°C. Pulse-echo technique was used for ultrasonic velocity measurements on Ni coated (16.59% AlN + 6.63% WC) samples. It is aimed to examine the change of physical, mechanical and ultrasonic properties of the obtained ceramic-metal composites depending on different sintering temperatures. In addition, the samples were characterized by mechanical and metallographic examination. The results show that the longitudinal and transverse ultrasonic velocity values and ultrasonic modulus (shear, bulk, Young’s etc.) values increase simultaneously with the increase of sintering temperature. The highest microhardness value was observed in composite samples sintered at 1400°C and its value was 1150.80 Hv. The increased strength is mainly due to grain refinement and strong interfacial bonding between Ni particles and AlN and WC matrix.

The Interfacial Reaction Traits of (Al63Cu25Fe12) 99Ce1 Quasicrystal-Enhanced Aluminum Matrix Composites Produced by Means of Hot Pressing

This study fabricated (Al63Cu25Fe12)99Ce1 quasicrystal-enhanced aluminum matrix composites using the hot-pressing method to investigate their interfacial reaction traits. Microstructure analysis revealed that at 490 °C for 30 min of hot-pressing, the interface between the matrix and reinforcement was clear and intact. Chemical diffusion between the I-phase and aluminum matrix during sintering led to the formation of Al7Cu2Fe, AlFe, and AlCu phases, which, with their uniform and fine distribution, significantly enhanced the alloy’s overall properties. Regarding compactness, it first increased and then decreased with different holding times, reaching a maximum of about 98.89% at 490 °C for 30 min. Mechanical property analysis showed that compressive strength initially rose and then fell with increasing sintering temperature. After 30 min at 490 °C, the reinforcement particles and matrix were tightly combined and evenly distributed, with a maximum compressive strength of around 790 MPa. Additionally, the diffusion dynamics of the transition layer were simulated. The reaction rate of the reaction layer increased with hot-pressing temperature and decreased with holding time. Selecting a lower temperature and appropriate holding time can control the reaction layer thickness to obtain composites with excellent properties. This research innovatively contributes to the preparation and property study of such composites, providing a basis for their further application.

Effect of Al2O3-SiO2 mass ratio and sintering temperature on the properties of water-soluble salt-based ceramic cores formed by binder jetting

Binder Jetting (BJ) technology, known for its cost-effectiveness and efficiency, is widely used for the rapid fabrication of complex ceramic cores. However, fabricating high-strength and water-soluble ceramic cores via BJ technology is particularly challenging due to the balance between mechanical properties and water solubility. In this work, BJ technology was employed to fabricate high-strength and water-soluble salt-based ceramic cores (SCC) regulated synergistically by Al2O3 and SiO2. The effects of the mass ratio of Al2O3 to SiO2 (A/S) and sintering temperature on the properties of Na2CO3-based samples were investigated, with detailed analyses of the regulation mechanism through thermodynamic, kinetic, and microstructural examinations. The results indicated that when A/S was 1:4, the bending strength of samples sintered at 760 °C for 60 min reached up to 62.38 MPa with good water collapsibility. Thermodynamic and kinetic analyses revealed that the formation of Na2SiO3 was prioritized over NaAlO2, and the content of Na2SiO3 as well as the proportion of liquid phase increased with the decrease of A/S and the increase of sintering temperature, resulting in the increase of sample density, as confirmed by microstructure analyses, which was the main strengthening mechanism of samples. Ultimately, complex-structure SCC samples were successfully fabricated. This study provides an insightful method for fabricating high-strength and water-soluble ceramic cores, with significant potential applications in the casting industry.

Effect of sintering temperature on microstructure and magnetic properties of ErFeO3 ceramics

ErFeO3 ceramics had been synthesized by the solid-state reaction method at a variety of sintering temperatures (1250, 1300, 1350, 1400, 1450, and 1500 °C). The microstructure, surface morphology, and elemental valence state of ErFeO3 polycrystalline ceramics were investigated using X-ray diffraction (XRD), Raman spectroscopy (Raman), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The study discovered that Fe3+ ions keep their valence, and all samples at temperatures ranging from 1300 to 1450 °C are in a pure phase. Within this range, increasing temperature widens the Fe-O-Fe bond angle, lengthens the Er-O bond, suppresses the super-exchange contact between the two ions via O2−, and diminishes the electromagnetic coupling effect. A Physical Property Measurement System (PPMS) was utilized to assess the magnetic properties of ErFeO3 polycrystalline ceramics. Ceramic samples sintered at 1300 °C showed spontaneous spin reorientation and a shift from ionic magnetic disorder to magnetic order. The magnetic hysteresis loops at temperatures before and after spin reorientation were examined. It was noted that the polycrystalline ceramic ErFeO3 underwent a transition in its magnetic configuration from Γ4 (Gx, Ay, Fz) to Γ2 (Fx, Cy, and Gz). As the sintering temperature increases, ErFeO3 polycrystalline ceramics lose their temperature adjustment point. This disrupts the spin reorientation of Er3+ and Fe3+ magnetic moments in the 89–102 K region. The secondary phase transition of ErFeO3 polycrystalline ceramics causes disorder, and the Néel temperature of Er3+ rises. This suggests that the sublattice field and magnetic ordering of Er3+ and Fe3+ are disturbed when the sintering temperature is raised. Consequently, 1300 °C is the optimal sintering temperature for ErFeO3 polycrystalline ceramics.

The Impact of the Final Sintering Temperature on the Microstructure and Dielectric Properties of Ba0.75Ca0.25TiO3 Perovskite Ceramics.

Ba0.75Ca0.25TiO3 ceramics were successfully synthesized by a simple solid-state reaction method. This study examined the influence of sintering temperature on the structure, microstructure, dielectric properties and electrical behavior of the material. The XRD analysis reveals that the tetragonal phase (P4mm) is dominant in all the synthesized materials, with those sintered at T = 1400 °C and T = 1450 °C being single-phase, while others exhibit a minor orthorhombic phase (Pbnm). Higher sintering temperatures promoted better grain boundary formation and larger grain sizes. The electric permittivity increased with temperature up to T = 1400 °C, followed by a sharp decline at T = 1450 °C. Additionally, the Curie temperature decreased with increasing sintering temperature, indicating changes in phase transition characteristics. Thermal analysis showed that higher sintering temperatures led to sharper heat capacity peaks, while pyroelectric and thermally stimulated depolarization currents were maximized at T = 1400 °C due to oxygen vacancies. These findings highlight the significant impact of sintering temperature on the material's structural and functional properties.

Synthesis of Sustainable Binary Calcium Monosilicate Ceramics from Bio-waste: Effect of Sintering Temperature on Microstructure and Electrical Properties

This study was conducted to synthesise calcium monosilicate ceramics using rice husks and raw eggshells and investigated the effect of sintering temperature on the physical,microstructure and electrical properties of the final product. The high content of calcium and silicon in eggshells and rice husks, respectively promote the use of waste materials in the production of calcium monosilicates by mixing in a molar ratio 1CaO:1SiO2 and fired at different sintering temperatures for 2 hours with a heating rate of 10°C/min. A good correlation between sintering temperature, structural, microstructure, and electrical properties of calcium silicate was observed. The structural and morphological evolutions were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with electron dispersive X-ray analysis (EDX). XRD analysis showed that the main crystalline phases of synthesised calcium monosilicate are pseudowollastonite (ICSD 98-005-2598) at 1250°C, and the phases of SiO2 also exist in different types of minerals. Besides, a small amount of larnite, Ca2SiO4 was traced at 1100°C and 1200°C. Fourier Transforms Infrared (FTIR) spectra showed the presence of characteristic functional groups in the precursor powder. In Nyquist plots, the summit frequency of the dominant arc decreases with increasing sintering temperatures. It may be attributed to the co-effect of the grain size and pore. A larger value of impedance at a lower frequency suggests an essential role of boundaries in governing the electrical properties of the sintered ceramics. As the sintering temperature increases, the microstructure of the sintered samples becomes denser while conductivity performance decreases. This is due to the reduction of particle interfaces and charge transfer.

Densification and properties of WC-CoCrFeNi/Co cemented carbide fabricated via spark plasma sintering

The spark plasma sintering (SPS) technique was used to employe WC-CoCrFeNi/Co cemented carbides, incorporating CoCrFeNi and Co as low-coercivity binder phases, resulting in the development of cemented carbides with exceptional mechanical properties. The densification mechanism varying with increasing sintering temperature and the effect of densification on the mechanical properties were investigated using the creep deformation model. In the temperature range of 1100 °C–1300 °C, the main factors contributing to densification behavior are particle rearrangement and grain boundary diffusion due to the viscous flow of the binder phase. The densification mechanism gradually transforms into dislocation climbing with increasing temperature. When the sintering temperature exceeded 1300 °C, the WC grain size increased significantly with increasing temperature and holding time, and the dominant mechanism for grain growth was grain boundary diffusion. The high densification resulted in a substantial increase in effective grain boundary area, thereby increasing both hardness and fracture toughness of the material. Benefiting from the fine grain strengthening effect of the high-entropy alloys (HEAs) and the excellent wettability of Co, a highly dense cemented carbide material with excellent hardness and fracture toughness is achieved at the sintering temperature of 1300 °C, characterized by a relative density of 99.3 %, a hardness of 2064.9 MPa, and a fracture toughness of 11.5 MPa m−2.

Evolution mechanism of Ti(C,N)-based cermet microstructure under microwave sintering

Experimental studies of microwave-sintered cermets were carried out at different sintering temperatures and holding times to investigate their microstructure evolution mechanism. Results of the study show that: (1) As sintering temperature increases, main microstructure evolution mechanisms of cermets are as follows: metal-phase melting, hard-phase skeleton filling of large pores in hard-phase skeletons, secondary rearrangement of the liquid phase (the liquid phase gradually fills the space between grains), and cooling down (precipitation–crystallization–reattachment); (2) As holding time increases, main microstructure evolution mechanisms of cermets are as follows: complete filling of large pores in the hard-phase skeleton, secondary rearrangement of the liquid phase, intense dissolution precipitation enhancing the formation of core-rim phase, and secondary homogeneous arrangement of the liquid phase. The special electromagnetic effects of microwave-sintered cermets and their influence on the sintering process were analyzed. It was found that both tip-discharge effect and hot-spot effect occurring during the microwave sintering process are conducive to the sintering process. The formation process of core-rim phase of cermets was also studied. Results show that: (1) Cermets form black core–white rim–grey rim structure via dissolution–precipitation and precipitation–crystallization phenomena; (2) Cermets form white core–grey rim structure through agglomeration of small particles, dissolution–precipitation, and precipitation–crystallization phenomena.

Study of the Sintering Process Behavior on Some Structural and Physical Properties of (Ni-47Ti-3Cu) Alloy Prepared by Powder Metallurgy

This research aims to prepare the alloy (Ni-47Ti-3Cu) using powder metallurgy techniques and study the sintering behavior of this alloy at different temperatures. Powders of nickel, titanium, and copper, were mixed to ensure homogeneity, then compacted under a pressure of (5ton) for (2 min) to obtain cohesive samples. The sintering process was carried out at temperatures of (1050, 950, 850, 750, 650) °C for 1 hour. The structural properties were studied using X-ray diffraction (XRD), and the physical properties (apparent density, bulk density, porosity, and water absorption) were examined using Archimedes' principle-based tests. The XRD results indicated the emergence of a new phase with a different crystalline structure from the elements used in the preparation of the models, identified as (TiCuNi2) with a rhombohedral crystal system, while the constituent elements of the alloy exhibited face-centered cubic (F.C.C) structures for nickel and copper and a hexagonal close-packed (H.C.P) structure for titanium. The physical examination results showed that both apparent and bulk densities increased with increasing sintering temperature, while porosity and water absorption decreased with increasing sintering temperature.

Effects of Ni cation ratio and sintering temperature on microstructure and electrical properties of NiMnCoO4-based ceramics

Negative temperature coefficient (NTC) thermistors as temperature sensors play an important role in various electrical/electronic devices and are widely applied in the fields such as, automotive sensor modules, home appliances and control applications. The electrical properties of NTC thermistors can be effectively controlled by regulating the content of their chemical components or changing the microstructures. Therefore, this study investigated the effects of Ni cation ratio and sintering temperature on microstructures, crystal structures, and electrical properties of NiMnCoO4-based ceramics. With increasing Ni content, it was found that sinterability of NiMnCoO4-based ceramics was decreased with forming rock-salt phase of NiO, resulting in degrading resistivity. Furthermore, the spinel structures were detected by X-ray diffraction analysis regardless of sintering temperatures. Notably, values of average grain size for sintered samples were increased with increasing sintering temperature. Besides, it was clarified that electrical properties were significantly influenced by average grain size. The room temperature resistivity was increased from approximately 300 kΩ⋅cm for the sintered sample at 1100°C to about 600 kΩ⋅cm for for the sintered sample at 1300oC. On the other hand, the B(25/85) constant was not significantly influenced by the sintering temperature. Accordingly, it is expected that the results of this study are useful for controlling electrical properties of MnCoNiO4-based ceramics.

Synthesis, Structure and Luminescence Properties of Mn-doped MgAl2O4 Red-Emitting Phosphors with Varying Sintering Temperature.

Oxide matrix red-emitting phosphors are deemed as excellent color converters for white light emitting diodes (WLEDs) and laser diodes (LDs). Manganese-doped MgAl2O4 powder was synthesized by a solid-state reaction method at different sintering temperatures. Microstructure shows that grain size is mainly in the range of 0.2-5μm, and grain agglomeration occurs with increased sintering temperature. XPS analysis indicates that the doped Mn ion exhibits a valence state of + 4 within the MgAl2O4 matrix. The diffraction peak of the phosphors is shifted by the sintering temperature, which affects lattice constant. Upon excitation by 300nm ultraviolet light, the samples emit asymmetric broadband red light within the range of 620-720nm, attributed to Mn4+ ion's transition from 2Eg to 4A2g states. With the increasing temperature, the main emission peak shifts from 677nm to 650nm, ascribed to the change in energy level (2Eg) resulting from the reduction of Al2O3 phase. Crystal field theory confirmed that Mn4+ ions are within a strong crystal field environment created by MgAl2O4 matrix. By affecting particle size and crystallinity, the sintering temperature influences the fluorescence lifetime of the Mn4+ ion. Notably, these red-emitting phosphors exhibits remarkable thermal stability as their emission intensity remains approximately at 58% of initial intensity even at elevated temperature (435K). Consequently, Mn4+: MgAl2O4 red-emitting phosphors with high thermal stability render them promising candidates for WLED applications.

Brownish Green Fired Clay Tiles Produced by Valorizing Green Glass Cullet and Sediment Soil

This paper aims to valorize waste materials for producing eco-friendly fired clay tiles. Green glass cullet and the water supply process waste; sediment soil have been utilized. In addition, local white clay is used to mix with waste materials for promoting the plasticity and easily forming of specimens. The Triaxial diagram has been employed to construct the formulas. Mixture’s formulation of this experiment consists of 23 formulas. Test samples are fired at temperature 950 °C. Physical properties of fired specimens are carried out and compared with Thailand Industrial Standards. The results show that formula A6 can pass TIS. 2508-2555 wall tiles of medium water absorption series. However, A6 only utilize 10% of sediment soil. Therefore, increasing sintering temperature to 1,050 °C for utilizing higher content of sediment soil has been examined. Twelve formulas of group A and C are selected to be further investigated. Results show that formula A6 and C6 can achieve TIS. 2508-2555. Formula C6 utilizing 30% and 60% of sediment soil and green glass cullet obtain the highest strength and lowest water absorption. Analyzing microstructure of this formula by Scanning Electron Microscope has found glassy phases. Furthermore, Wollastonite 2M, Nepheline and Albite are identified by X-Ray Diffractometer. It can be summarized that sediment soil mixed up with green glass cullet and local white clay can develop brownish green color fired clay tiles which can be further applied to the production of local ceramic factory.

Effect of temperature on the microstructure and mechanical properties of TiC/Fe matrix composites fabricated by spark plasma sintering

The effects of sintering temperatures on the microstructures and mechanical properties of titanium carbide particles reinforced iron matrix composites (TiC/Fe MCs) fabricated by the spark plasma sintering (SPS) process with pure element powders have been systematically investigated. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron back scattering diffractometer (EBSD), and energy dispersive spectroscopy (EDS) have been conducted for microstructural analysis. The results show that with increasing sintering temperatures, the porosity of the composites initially decreases and then increases. Simultaneously, the grain size gradually diminishes while element diffusion becomes more uniform. Upon reaching a critical sintering temperature (1120 °C), the original grain size disappears and carbides undergo decomposition and reprecipitation to reach an equilibrium state, with which optimal comprehensive properties can be achieved (porosity decreases to a minimum of 3.85%, grain size of 2.69 μm, Vickers hardness reaches 595 HV0.5, bending strength is at 662 MPa, coefficient of friction is at 0.74, and wear loss to 0.21 mg). These property enhancements have been attributed to reduced porosity in the composites, decreased grain size, and improved anchoring effect of carbides within the matrix. Additionally, the primary fracture mechanisms and wear mechanisms of TiC/Fe MCs with different process parameters have been analyzed. When the temperature is below 1080 °C, intergranular fracture predominates, whereas transgranular and ductile fractures become predominant above this threshold. When the temperature is below 1120 °C, fatigue wear, oxidation wear, and abrasive wear are predominantly observed. Conversely, when the temperature exceeds 1120 °C, oxidation wear and abrasive wear become the primary mechanisms.

Preparation of K0.48Na0.52NbO3 & akermanite composite ceramics with biodegradability for cancellous bone repair by digital light processing

Lead-free piezoelectric ceramics can generate electrical signals to promote bone defect repair, but they suffer from low bioreactivity. In this study, K0.48Na0.52NbO3 & akermanite composite ceramic (KNN & AK) was prepared using digital light processing (DLP). The influence of sintering temperature and AK content was investigated. With the increase of sintering temperature, the piezoelectric coefficient d33 of the composite ceramics first increased and then decreased, reaching a maximum of 7.80 pC/N at 1070 °C. The doping of AK would lead to a significant decrease in the piezoelectric property, and the AK content should not exceed 10 wt% to achieve the piezoelectric coefficient of human bone. After immersion in Tris-HCl solution for 28 days, the weight loss rate of the composite ceramics doped with 15 wt% AK could reach 8.36 %. The combination of KNN and AK promotes the application of piezoelectric bone scaffolds in the field of bone repair.

Effect of sintering temperature and holding time on structure and properties of Li1.5Ga0.5Ti1.5(PO4)3 electrolyte with fast ionic conductivity

Li1.5Ga0.5Ti1.5(PO4)3 (LGTP) is recognized as a promising solid electrolyte material for lithium ions. In this work, LGTP solid electrolyte materials were prepared under different process conditions to explore the effects of sintering temperature and holding time on relative density, phase composition, microstructure, bulk conductivity, and total conductivity. In the impedance test under frequency of 1−106 Hz, the bulk conductivity of the samples increased with increasing sintering temperature, and the total conductivity first increased and then decreased. SEM results showed that the average grain size in the ceramics was controlled by the sintering temperature, which increased from (0.54±0.01) μm to (1.21±0.01) μm when the temperature changed from 750 to 950 °C. The relative density of the ceramics increased and then decreased with increasing temperature as the porosity increased. The holding time had little effect on the grain size growth or sample density, but an extended holding time resulted in crack generation that served to reduce the conductivity of the solid electrolyte.

Sintering temperature dependent characterization of Ni nano ferrite with the optimization of frequency dependent properties

Ni ferrite is becoming a prominent candidate for high frequency applications. To find the best performance of Ni ferrite for high frequency devices, NiFe2O4 ferrites are synthesized by co-precipitation method at five distinct sintering temperatures (TS = 500 °C, 700 °C, 850 °C, 1000 °C, and 1200 °C). The structural properties of the synthesized samples are characterized by x-ray diffraction (XRD) with Rietveld refinement analysis. The grain formation of the ferrites is observed by field emission scanning electron microscopy (FESEM) and the gradual increase in grain size is noticed with the increment of sintering temperature. The frequency dependent properties are studied by an impedance analyzer. The real permeability values of the samples are stable in a wide frequency range (100 Hz to 100 MHz) and the imaginary permeability values are decreased at lower frequency region. It can be seen that the real part of magnetic permeability increases significantly with sintering temperature. The real and imaginary dielectric properties are reduced at the initial applied field and become constant at higher frequencies. The magnetic quality factor and dielectric quality factor are enhanced with the increase of sintering temperature. Frequency dependent properties confirm that these ferrites are strong candidates for potential high frequency applications. Finally, it is found that, comparatively a higher sintering temperature is better for permeability properties, and a lower sintering temperature is better for dielectric properties.

Improved precision and mechanical properties of 3D‐printed silica ceramics via sintering temperature optimization

AbstractCeramic cores are the key components of precision casting hollow turbine blades, and 3D‐printed silica‐based ceramic cores are crucial to the development of the aerospace industry. However, silica‐based ceramic cores have problems in terms of mechanical properties and friction properties. In this paper, silica ceramics were prepared by stereolithography‐based 3D printing technology and processed at different sintering temperatures. The effect of sintering temperature on the microstructure, physical–mechanical properties, and friction and wear properties of the silica ceramics was investigated. The results show that, with the increase of sintering temperature, the average particle size and bulk density of the samples increased, while the open porosity and layer thickness decreased. The surface of ceramics became more and more flat with the increase in temperature. The flexural strength first increased with increasing temperature, and then suddenly decreased at 1350°C. The average surface roughness decreased with increasing temperature. The wear of the material decreased with increasing sintering temperature and increased at 1350°C. The optimum sintering temperatures were 1250°C and 1300°C, giving a flexural strength of 23.18 and 23.25 MPa, bulk density of 1.72 and 1.78 g/cm3, and open porosity of 24.49% and 23.66%, respectively.

Effect of sintering temperature on mechanical properties of WC-cBN-SiCw composites with multi-scale and multi-morphology toughening strategy

The binderless WC cemented carbide was synthesized with multi-scale and multi-morphology toughening strategy by Spark Plasma Sintering. The influence of sintering temperature on the mechanical properties of WC-cBN-SiCw was investigated. The result showed that the Vickers hardness and fracture toughness initially increase and then decrease with the increase of sintering temperature. As the sintering temperature reaches 1300℃, the best Vickers hardness and fracture toughness can be obtained, 12.8 GPa and 10.6 MPa.m1/2 respectively. The toughening mechanism can be attributed to the strong and weak mixed interface characteristic constructed by micro and nano particles, which induce crack deflection and crack bridging. Meanwhile, the adhesion of nanoparticles on SiC whisker enhances the resistance of whisker pull out, which promotes the consumption of fracture energy.

Microstructure and mechanical properties of (Ti, W, Mo, Nb, Ta) (C0.78, N0.22) high entropy cermets with 5–25 wt% Co–Ni binders

In this study, high entropy (Ti0.6,W0.1,Mo0.1,Nb0.1,Ta0.1)(C0.78,N0.22) ceramics (HECN) powders were synthesized by carbothermal reduction nitridation. (100-x) HECN-(x/2) Co-(x/2) Ni (x = 5–25 wt%) cermet was prepared by vacuum sintering. The relationship between microstructure and mechanical properties of HECN-based cermet sintered at 1450 °C and 1500 °C was studied. The results show that the second phase (W,Mo,Ti)3+x(Co, Ni)3−xC appears at both sintering temperatures, and its content decreases with the increase of binder Co, Ni content and sintering temperature; At the same time, the grain size of the hard phase of the cermet grows with the increase of Co and Ni content. In terms of mechanical properties, at both sintering temperatures, the cermet showed a decrease in hardness and an increase in fracture toughness with the increase of Co and Ni content, while the bending strength increased and then decreased. Among them, when the content of Co and Ni is 20 wt%, the bending strength of HECN-based cermet sintered at 1450 °C is the best, and the bending strength reaches 1640 MPa. This is attributed to the combined influence of many elements in high entropy cermet, which on the one hand leads to serious lattice distortion; On the other hand, improving the wettability and density of the cermet has a strengthening effect on the cermet. In addition, with the increase in Co and Ni content, the plastic deformation of the bond phase will inhibit crack propagation. The main paths are crack deflection and crack bridging, which increase the energy required for crack propagation and lead to a gradual increase in fracture toughness.

Evolution of microstructure and mechanical properties of TiB2-7.5 wt.% WC-based cermets sintered at different temperatures

The evolution of microstructure and mechanical properties of TiB2–7.5 wt% WC-based cermets sintered at different temperatures were investigated. The results showed that eutectic liquid phase appeared at around 1335 °C, indicating that solid-phase sintering occurred below that temperature, while liquid-phase sintering occurred above that temperature. TiB2, W2CoB2, WB and CoNi phases were detected in the XRD patterns of cermets sintered at different temperatures, and TEM analysis showed the presence of TiC phase. So the following chemical reaction should occur: TiB2 + WC + Co → W2CoB2 + WB + TiC. The TiB2 core - (Ti, W, Co, Ni)(B, C) rim phase were observed in the cermet sintered at 1397 °C. As the increase of sintering temperature, the solubility of WC and TiB2 in CoNi binder phase, and the number of core-rim structure hard phase particles increased. The formation of core-rim structure enhanced the interfacial bonding strength between TiB2 phase and CoNi binder, which was beneficial for improving the strength and toughness of cermets. The cermets sintered at 1465 °C had good comprehensive mechanical properties, with a relative density of 99.62%, a hardness of 17.34 ± 0.43 GPa, a transversal rupture strength of 2038 ± 53 MPa, and an indentation fracture toughness of 12.15 ± 0.32 MPa·m1/2.