Spark Plasma Sintering Process Research Articles

Interface Optimization and Thermal Conductivity of Cu/Diamond Composites by Spark Plasma Sintering Process.

Cu/Diamond (Cu/Dia) composites are regarded as next-generation thermal dissipation materials and hold tremendous potential for use in future high-power electronic devices. The interface structure between the Cu matrix and the diamond has a significant impact on the thermophysical properties of the composite materials. In this study, Cu/Dia composite materials were fabricated using the Spark Plasma Sintering (SPS) process. The results indicate that the agglomeration of diamond particles decreases with increasing particle size and that a uniform distribution is achieved at 200 μm. With an increase in the sintering temperature, the interface bonding is first optimized and then weakened, with the optimal sintering temperature being 900 °C. The addition of Cr to the Cu matrix leads to the formation of Cr7C3 after sintering, which enhances the relative density and bonding strength at the interface, transitioning it from a physical bond to a metallurgical bond. Optimizing the diamond particle size increased the thermal conductivity from 310 W/m K to 386 W/m K, while further optimizing the interface led to a significant increase to 516 W/m K, representing an overall improvement of approximately 66%.

Thermoelectric properties of GeTe-based composites prepared by spark plasma sintering containing Bi/Sb additive

Spark plasma sintering (SPS) is often used to prepare bulk thermoelectric (TE) materials, and the application of additives during the process may have a unique effect on constructing multiphase structures. The additives with low melting points can be often extruded or react with the matrix during the SPS process, leaving dense dislocations or multiphase structures to optimize the TE performance. In this paper, high-performance GeTe-based composites were prepared by SPS containing Bi or Sb additive. During the SPS process (sintering temperature ∼773 K), the Bi (melting point ∼544 K) or Sb (∼904 K) additive have the liquid-solid/solid-solid reaction with the GeTe matrix, respectively. The chemical reactions lead to the composite structures of the matrix and pseudo-binary alloy (GeTe)x(Bi2Te3) or (GeTe)y(Sb2Te3) with 7 ≤ (x, y) ≤ 9, resulting in a significant increase in the Seebeck coefficient by the energy filtering effect and the reduction of thermal conductivity by enhancing the phonons scattering. The influence of the Sb additive is better than that of Bi, therefore, the sample with 1 wt% Sb has a ZTmax value of 1.49 at 685 K, ∼157 % higher than that of the matrix (0.58). This study shows that SPS with appropriate additives is an effective method to prepare high-performance GeTe-based TE composites.

High-temperature spark plasma sintering of h-BN composites reinforced with carbon nanotubes, carbon fibers, and graphene nanoplates

In this study, two h-BN-based composites reinforced with carbon fibers (CF) and carbon fibers/carbon nanotubes (CNTs)/graphene nanoplates (GNPs) have been produced successfully through a high-temperature spark plasma sintering. 1 Wt.% short carbon fibers (length of 5 mm) with 0.1 Wt.% of CNTs and also 0.1 Wt.% of GNPs as hybrid composite were mixed through a simple mixing method including a high energy sonicating and stirring on the hot plate in ethanol media until drying. Moreover, h-BN/1 Wt. % CF composite was mixed with a similar method to compare impacts of CNTs and GNPs addition on the mechanical properties and microstructure of h-BN/CF composite. The high-temperature spark plasma sintering processes were performed at vacuum conditions of almost 20-25 MPa with a starting pressure of 10 and a final applied pressure of 50 MPa at a maximum temperature of 1900˚C. Both prepared samples showed near full densification of higher than 98.1 % of the theoretical density determined by Archimedes’ principle. Investigation of the crystalline phases by XRD represented only related peaks to h-BN. The FESEM images indicated an almost uniform distribution of reinforcement in the h-BN matrix. Furthermore, the polished surface of the provided samples showed only the pulled-out carbon fibers effects while the fracture surfaces confirmed the presence of CF and it’s tunneling effects. The obtained mechanical properties revealed 273±12 MPa of bending strength, 1.32±0.1 GPa of Vickers hardness, and 4.79±0.2 MPa.m0.5 fracture toughness for the prepared hybrid composite.

Microstructure, Mechanical, and Tribological Behaviour of Spark Plasma Sintered TiN, TiC, TiCN, TaN, and NbN Ceramic Coatings on Titanium Substrate

Titanium (Ti) is widely used in structural, maritime, aerospace, and biomedical applications because of its outstanding strength-to-weight ratio, superior corrosion resistance, and excellent biocompatibility. However, the lower surface hardness and inferior wear resistance of the Ti and Ti alloys limit their industrial applications. Coating Ti surfaces can initiate new possibilities to give unique characteristics with significant improvement in the Ti component’s functionality. The current research designed and synthesized titanium nitride (TiN), titanium carbide (TiC), titanium carbonitride (TiCN), tantalum nitride (TaN), and niobium nitride (NbN) ceramic coating layers (400 µm) over a Ti substrate using a spark plasma sintering process (SPS). The coatings on the Ti substrate were compact and consolidated at an SPS temperature of 1500 °C, pressure of 50 MPa, and 5 min of holding time in a controlled argon atmosphere. Microstructure investigation revealed a defect-less coating-substrate interface formation with a transition/diffusion zone ranging from 10 µm to 20 µm. Among all of the ceramic coatings, titanium carbide showed the highest improvement in surface hardness, equal to 1817 ± 25 HV, and the lowest coefficient of friction, equal to 0.28 for NbN.

Mechanical characteristics of dual‐phase medium‐entropy boride/carbide ceramics synthesized through SPS

AbstractMaterial scientists constantly look for new compounds with exceptional properties to meet the ever‐changing technology and industry needs. Hereby, the dual‐phase medium‐entropy ceramics have fabricated by employing high‐energy ball milling (HEBM) and spark plasma sintering (SPS) techniques on commercial boride and carbide powders of IVB group metals. The boride and carbide powders have undergone 3‐hour milling in a planetary ball mill, followed by SPS processing at 1800°C and 2000°C under 30 MPa uniaxial pressure for 10 min. The milled powders and SPS'ed ceramics have been characterized, focusing on composition, density, and microstructure using X‐ray diffractometry (XRD) and scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS). Microhardness and sliding wear tests have also been performed on the SPS'ed ceramics. The systematic analysis of the characterization results has revealed that the microstructural evolution and mechanical properties of the dual‐phase ceramics have developed to a comparable level with the single‐phase ceramics, regardless of the sintering temperature. In fact, the dual‐phase ceramics sintered at 1800°C come to the forefront due to the superior hardness and fracture toughness values (∼ 16 GPa and ∼ 5.4 MPa.m1/2).

Spark Plasma Sintering Preparation of Tungsten Carbide-Reinforced Iron-Based Composite Materials: Wear Resistance Performance and Mechanism.

The spark plasma sintering (SPS) process was used to create iron-based composites reinforced with tungsten carbide (WC) particles of various morphologies, and the effect of WC particle morphology on material wear resistance was systematically investigated. The experiment revealed that the addition of non-spherical WC (CTC-A) significantly altered the composites' friction coefficient, wear morphology, and wear mechanism. As the CTC-A content increased, the composites' wear rate decreased at first, then increased, and then decreased again. Composites with a CTC-A concentration of 10% had a minimum wear rate of 2.7 × 10-6 mm3/(N·m) and peaked at 20%. SEM analysis indicated that the wear mechanism gradually changed from initial oxidative wear to abrasive wear as the CTC-A content increased, and the wear morphology transitioned from smooth to rough with the appearance of numerous abrasives and cracks. The study demonstrated that the low content of non-spherical WC particles during sintering significantly increased the hardness of the matrix by forming carbide phases, while a high content led to increased surface roughness, inducing abrasive wear and reducing wear performance. These findings provide a significant theoretical basis and practical guidance for optimizing the design of iron-based composites.

Tribological Properties of SPS Reactive Sintered Al/MoS2 Composites

In search of opportunities to improve mechanical properties and abrasion resistance, composites based on aluminum reinforced with MoS2 particles were produced. The authors’ previous research indicated the possibility of obtaining hard dispersion precipitates of the Al12Mo intermetallic phase as a result of the reaction of the composite components at a temperature exceeding 550 °C during the SPS (Spark Plasma Sintering) process. This work focused on optimizing the SPS consolidation process and assessing the microstructure and mechanical properties of the obtained materials. A series of experiments proved that by increasing the amount of the strengthening phase and increasing the process temperature, a significant amount of Al12Mo and Al5Mo strengthening phases is produced. Exceptionally good dispersion of reinforcing particles and the presence of layered MoS2 crystals, while ensuring optimal parameters of the synthesis process, lead to a change in friction mechanisms and improved abrasion resistance through an approximately 30-fold decrease in the wear factor.

Preparation of WC-Co cemented carbide by spark plasma sintering: Microstructure evolution, mechanical properties and densification mechanism

In this study, Spark Plasma Sintering (SPS) was utilized to fabricate fine-grained cemented carbides, and an orthogonal experimental design was employed to examine the influence of holding temperature (1100 °C, 1200 °C, 1300 °C) and holding time (5, 10, and 15 min) on the performance of WC-10Co cemented carbide specimens. Compared with conventional sintering methods, this work achieved the production of samples with enhanced overall performance at lower temperatures and shorter durations. Specifically, under the conditions of a holding temperature of 1300 °C and a holding time of 5 min, the resulting specimens exhibited a density of 14.64 g/cm3, a hardness of 91.29 HRA, a fracture toughness of 16.39 MPa·m½, and a transverse rupture strength of 2398 MPa. The microstructural analysis revealed that as the holding temperature increased, the Co phase in the specimens underwent a transformation from its initial powder form to banded cobalt and subsequently to slit-shaped cobalt. It was found that the presence of banded cobalt effectively hinders crack propagation, whereas slit-shaped cobalt is more effective in preventing crack initiation, thus impacting the overall performance of the specimens. By analyzing the sintering curves and microstructures, the densification mechanisms during SPS sintering of WC-Co cemented carbides were elucidated. The study concluded that the state changes of the Co phase play a significant role in the densification behavior, final microstructure, and properties of the sintered material. These findings offer valuable insights for understanding and optimizing the SPS process.

Microstructure evolution and mechanical properties of CoCrFeMnNi HEA-MXene composites prepared by spark plasma sintering

In this work, the influence of different MXene weight percentages (0, 2, 4, 6 & 10 wt%) on the microstructure, wear behavior, and mechanical properties of CrMnFeCoNi High Entropy Alloy (HEA) were investigated. The CrMnFeCoNi HEA powder and Ti3C2Tx MXene phase were prepared by the gas atomization process and selective etching of the aluminum layer of MAX phase (Ti3AlC2), respectively. Bulk samples of CrMnFeCoNi HEA and HEA matrix-MXene composites were prepared by spark plasma sintering (SPS) using a mixture of CrMnFeCoNi HEA powder that contained 2 wt%, 4 wt%, 6 wt%, 10 wt% of MXene phase. The microstructure evolution, phase structure, and compressive mechanical properties of the samples were investigated at room temperature. It was observed that the CrMnFeCoNi HEA forms a single-phase FCC structure after the gas atomization and SPS process, while the microstructure of the HEA-MXene composites consisted of FCC and HCP phases. The fractions of the MXene phase played important roles in the nanostructural evolution and grain refinement of the HEA-MXene composites. The results of mechanical tests indicated that the micro-hardness of CrMnFeCoNi increased from 205.8 HV to 617.6 HV and the yield strength increased from 390 MPa to 1403 MPa with the addition of 10 wt% MXene phase. Moreover, the addition of MXene led to a significant increase in wear resistance and a decrease in the coefficient of friction. The attractive mechanical properties of the HEA-MXene composites were attributed to the grain refinement effect induced by the MXene phase.

Novel insights into the synthesis and tribo-mechanical performance of high-entropy (Hf0.2Zr0.2Ti0.2W0.2Mo0.2)B2 ceramics

High-entropy (Hf0.2Zr0.2Ti0.2W0.2Mo0.2)B2 ceramics were synthesized using a two-step spark plasma sintering process, with densification at 1600 °C followed by sintering at 1850 °C. This method produced dense materials with excellent mechanical and tribological properties. Hardness values ranged from 18.85 GPa to 39.65 GPa, with a maximum Young’s modulus of 319 GPa. Micro-scratch tests showed high resistance to plastic deformation and minimal surface damage, highlighting durability under mechanical stress. Tribological tests at 15 N and 20 N loads demonstrated exceptional wear resistance, attributed to hard primary phases and lubricating soft secondary phases. These findings confirm the material’s robustness and show the effectiveness of the two-step synthesis in optimizing microstructure and enhancing properties, making it suitable for high-stress and wear-intensive applications.

Response surface methodology and process optimization of spark plasma sintered parameters of Ti20Al20Cr5Nb5Ni19Cu12Co19 high entropy alloy

Study was carried out on the effect of milling and sintering process parameters on the relative density and microhardness property of a septenary non-equiatomic Ti20Al20Cr5Nb5Ni19Cu12Co19 high entropy alloy fabricated via spark plasma sintering (SPS) process at 100 °C/min constant heating rate, 5 min dwell time, and at a pressure of 50 MPa. A predictive model was developed through response surface methodology (RSM) using the SPS sintering temperature (ST) and milling time (MT) as the process variables. In order to reduce the number of experimental runs, the design of experiment (DOE) technique was used, to eventually avoid the trial-and-error process associated with conventional experimental procedures. The user-defined design (UDD) of the RSM was used to forecast the optimal operating parameters, and the outcome was validated by experiments. Findings indicate that MT and ST are important in achieving high densification, which leads to high densification and mechanical properties. Optimization model shows that, at MT of 7.20115 h and ST of 899.742 °C, desirable responses of 99.9 % relative density, percentage porosity of 0.0999994 % and a micro-hardness value of 835.21 HV can be attained.

Structural Design and Mechanical Properties Analysis of Laminated SiAlON Ceramic Tool Materials

Based on finite element simulation analysis, laminated ceramic tool materials with different structures were designed and the effect of laminated structure on tool state was investigated. Residual stresses in ceramic tool materials increase with the number of layers and layer–thickness ratio. Based on the simulation results, SiAlON-SiC-SiCw/SiAlON-Al2O3 ceramic tool materials (SCWAs) were prepared using the spark plasma sintering process, and the influence of residual stress on the mechanical properties and microstructure of laminated ceramic tool materials was studied. The mechanical properties of ceramic materials were significantly improved under the effect of residual stresses. The fracture toughness of SCWA4 with 7 layers and a layer–thickness ratio of 6 was 6.02 ± 0.19 MPa·m1/2, and the front and side flexural strengths were 602 ± 19 MPa and 595 ± 17 MPa, 36.3% and 39.0% higher than homogeneous SiAlON ceramics, respectively.

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.

Physical and Mechanical Characterization of Ti50Ni(50−X)FeX Shape Memory Alloy Fabricated by Spark Plasma Sintering Process

Physical and Mechanical Characterization of Ti50Ni(50−X)FeX Shape Memory Alloy Fabricated by Spark Plasma Sintering Process

Enhanced properties of hard metal WC-Ni processed from nanostructured powders

In this study, we investigated the effects of nanostructured composite powders (WC-Ni), nickel binder content, and sintering techniques on the morphology and mechanical properties of tungsten carbide. An alternative low-temperature gas-solid reaction route with a short reaction time was employed to produce nanostructured composite powders with 5 and 15 wt% Ni. The powders were consolidated using spark plasma sintering (SPS) and conventional vacuum furnace sintering at temperatures of 1350 °C and 1450 °C. The composite powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and particle size measurements. The expansion/contraction of the compacted nanocomposite powders was studied through dilatometric analysis. The composite powders exhibited a uniform distribution of Ni, in both compositions. For the WC-5 wt% Ni nanocomposite powders, the average crystallite sizes for WC and Ni were 41.6 nm and 46.2 nm, respectively. While, for the WC-15 wt% Ni nanocomposite, the crystallite sizes for WC and Ni were 45.6 and 38.4 nm. The sintered composites were evaluated through XRD, SEM, measurements of density and Vickers hardness. The enhanced sinterability of the nanostructured powders enabled their consolidation into (WC-Ni) hard metal with densities approaching the theoretical relative density of 96.07 %, even with low binder content (5 wt% Ni). This is attributed to the uniform distribution of Ni and an extensive Ni-WC interface present prior to sintering. The SPS process at 1350 °C produced sintered bodies (WC-5 wt% Ni and WC-15 wt% Ni) with higher Vickers hardness (2322 HV and 1512 HV, respectively) and superior microstructural quality compared to samples produced by conventional vacuum furnace techniques. These results demonstrated that the mechanical properties of the system WC-Ni processed by SPS are superior to those obtained by vacuum furnace. Therefore, WC-Ni hard metals processed by this approach is a promising alternative to conventional hard metals (WC-Co) for a wide range of applications.

Tribological behavior and mechanism of Ti3SiC2/Cu composites in a wide temperature range under lubrication condition

Preparation of Ti3SiC2/Cu composites using Spark Plasma Sintering (SPS) process. The friction and wear behavior of Ti3SiC2/Cu-45# steel tribo-pair under lubrication conditions was investigated in a wide temperatures range. The results demonstrated that the influence of temperature on the tribological properties of the Ti3SiC2/Cu-45# steel tribo-pair under lubrication condition was characterized by a continuous transition from a lubricant to an oxide film. At 200 ℃, mobility of the lubricant increased and the friction interface was in the boundary lubrication state. As the temperature increased, the base oil in the lubricant rapidly evaporated, causing to solidification of the lubricant, and the friction interface formed the friction oxide film. The mechanisms of friction and wear were primarily abrasive wear and tribo-oxidation wear.

Comparative study of microstructure and mechanical properties of Mg/B4C composites: Influence of sintering method and temperature

This present work compares the effect of heating methods including microwave and spark plasma sintering (SPS) process on the microstructure and mechanical properties of Mg–B4C. 5 wt%B4C mixed with Mg powders through high-energy mixer mill for 10 min at ethanol media. After mixing, the green bodies were prepared by uniaxially pressing the mixture. The microwave heating was done at sintering temperatures of 600, 650 and 700 °C without soaking time in graphite bed. While, in the case of SPS, the mixture of the powders was directly inserted into a graphite mold and sintering process was performed at 450 °C with initial and final pressures of 10 and 30 MPa at vacuum condition of 17 Pa, sequentially. The corresponding XRD patterns revealed Mg and B4C crystalline phase alongside the reaction product of MgB2 and also MgO byproduct. The FESEM investigations depict uniform distribution of B4C reinforcements at the Mg matrix. Moreover, increasing microwave sintering temperature led to decreasing pores at the microstructure of the prepared sample. The microstructure of SPSed sample revealed almost full densification compared to that of the microwave processed samples at all the sintering temperatures applied. Also, The XPS results show the presence of Mg, O, C and B elements on the surface of prepared composite, and HRTEM with HAADF-STEM images were obtained to study the interface of matrix and reinforcement. The highest bending strength and Vickers hardness of 116 ± 6 Hv and 231 ± 11 MPa were obtained for SPSed sample as well as for the highest relative density. Although the microwave sample was sintered at 700 °C at low pressure, sintering method demonstrated considerable mechanical properties in comparison to SPSed specimen, indicating a successful preparation method as a low-cost, energy- and time-saving process.

Microstructural evolution and mechanical behavior of WC–4wt.%TiC–3wt.%TaC–12wt.%Co refractory cermet consolidated by spark plasma sintering of mechanically activated powder mixtures

The paper studied the structural features and physicomechanical properties of the WC–4wt.%TiC–3wt.%TaC–12wt.%Co composite refractory hard alloy system obtained by spark plasma sintering (SPS) from a preliminarily mechanically activated powder. It has been shown that preliminary mechanical activation in a planetary mill contributed to the comminution of agglomerates and the formation of a monomodal particle size distribution with a predominance of the submicron fraction, which intensifies the densification processes during subsequent consolidation by the SPS method. Kinetic analysis of the SPS process showed a two-stage sintering pattern with intense densification at temperatures above 790 °C due to rearrangement of WC, TiC, TaC particles and melting of the cobalt binder. It has been found that the SPS method does not lead to the formation of undesirable secondary phases in the entire sintering temperature range. A sintering temperature of 1200 °C is optimal for achieving the best structural homogeneity, density and mechanical properties, providing optimal distribution of carbide phases and the cobalt binder. The microstructure of the sample obtained at 1200 °C represents a refractory skeleton of WC grains with TiC and TaC carbide particles uniformly distributed throughout the volume. Improved fluidity of the melted cobalt binder and its mobile redistribution contribute to increased compactness of the structure and reduced porosity of the material. Samples sintered at 1200 °C possess high physicomechanical characteristics: relative density 99.99 %, hardness HV30 1623.2, bending strength 1125.1 MPa, fracture toughness 10.5 MN⋅m1/2. The abrasive wear resistance of a newly synthesized hard material was evaluated through a turning operation. Results showed durability, indicating promise for cutting tool applications and the need for further research to fully characterize the performance of this novel material.

Comparison of two methods for achieving table-like magnetic entropy change in Eu-Ga-Ge clathrates

A novel method has been developed to efficiently produce composites of Eu-Ga-Ge clathrates through the process of spark plasma sintering (SPS) under varying pressures, temperatures, and times. This technique enables the adjustment of the α and β phase ratios, thereby allowing for the fine-tuning of material properties. The resulting composite exhibits a cohesive growth of both phases rather than a mere mechanical mixture, making it suitable not only for enhancing magnetic applications but also for improving various other physical properties including thermoelectric characteristics. The article focuses on the investigation of magnetocaloric properties in composites with different phase ratios. Remarkably, it was observed that an appropriately balanced ratio between the two phases yields a distinct table-like curve depicting magnetic entropy change, consequently leading to a enhanced refrigeration capacity (RC). Additionally, a hybrid sample was obtained through the mechanical mixing of several Eu-Ga-Ge β phases with different Tc values. The hybrid also exhibits a magnetic entropy change curve with a table-like shape. A comparative analysis between these two methods was conducted.

Synergistic-strengthening strategy induce excellent electrical and mechanical properties in Cu/AlCrCuFeNi2.5 composites

A novel high-strength conductive Cu-based composite, utilizing AlCrCuFeNi2.5 (Ni2.5) high-entropy alloy particles as the reinforcing phase, is synthesized through a combination of ball milling and spark plasma sintering processes. The mechanical and electrical properties of the composites are optimized by adjusting the composition. Under the synergistic effect of multiple strengthening mechanisms, the fabricated Cu-20 wt% Ni2.5 composites achieve an exceptional compressive strength of 920 MPa while maintaining an electrical conductivity of 44.3 % IACS (International Standard Copper Standard). The establishment of robust interface bonding between Ni2.5 reinforcement and Cu matrix stands as a pivotal assurance for the holistic performance of composites. Ni2.5 HEA is distinguished by good plasticity and high strength compared with traditional brittle reinforcements. An insight into the differences brought about by the distinctive dual-phase structure in terms of interfacial bonding, crack propagation, and performance is provided. It paves the way for selecting and projecting the composites for electrical contact applications, ushering in a realm of fresh possibilities.