Plasma Sintering Method Research Articles

Synthesis and Microstructure Characterization of Fe-Cr-Al Alloys Developed by Powder Metallurgy Technique with Plasma Sintering Method

Synthesis of Fe-Cr-Al alloy by powder metallurgy method was developed to produce a bioimplant material with a low modulus of elasticity. Microstructure characterization and phase identification were carried out to support the development of bone implant material research. The alloys were synthesized with the elemental composition of 16 Cr (wt%) that was added with Al in variations of 3, 6, and 10 (wt%). The synthesis was carried out by an exceptional combination of mixing and mechanical milling, cold compacting and consolidating with a special method using the APS (Arc Plasma Sintering) apparatus. Microstructure characterization and phase identification were analyzed by SEM-EDS and XRD tests. The microstructure showed relatively homogeneous fine grain with small porosity of around 80 %. Refinement of the XRD peak pattern revealed the formation of the Fe-Cr main phase followed by the Fe-Al phase with Al as the solid solution. The hardness test showed a high hardness level with a maximum for Fe-16Cr-6Al (wt%) of around 160 VHN (Vickers Hardness Number). The quantity of Fe-Cr phase and the composition of Al influenced the hardness of the alloy.

Titanium matrix composites reinforced with biogenic filler

Novel metal matrix composites (MMCs) have been fabricated with Ti6Al4V matrix and a biogenic ceramic filler in the form of diatomaceous earth (DE). Mixtures of DE and Ti6Al4V powders were consolidated by the spark plasma sintering (SPS) method. Microstructure of the consolidated samples has been investigated with microscopic techniques and XRD. Thermomechanical characteristics have been obtained using small-sample techniques. The results obtained indicate that the fabricated composites show outstanding mechanical and thermal properties due to synergic effects between the filler and the matrix (beyond the rule of mixtures).

Study of the effect of continuous loading and compaction on the electrical resistance of powder materials

The electrical conductivity of powder media depends on the composition, impurities, oxide films, morphology and the nature of the contact surface. We present the results of studying the electrical resistance of powder materials and their compounds under continuous loading by the four-contact method. The electrical resistance is determined using a special experimental cell. Industrial powders Al (ASD-1), Ti (PTK), Hf (GFM-1), soot and their mixtures, as well as TaC and HfC powders obtained by self-propagating high-temperature synthesis were studied. It is shown that an increase in the mechanical pressure up to 80 MPa leads to a decrease in the electrical resistance of the materials under study. The morphology of the particles (spherical or fragmentary shape), their dispersion affects the quality of the contact surface and, accordingly, the magnitude of the electrical resistance. Moreover, the electrical resistance of the material depends on the degree of cleaning of the particle surface from oxide films. The proposed method in combination with other analytical methods used for studying powder media allows us to reveal the regularities of this relationship, characteristic of all morphological features, composition and electrophysical properties of powders of various compositions under loading conditions. The results obtained can be used to select the optimal characteristics of consolidation by electric current depending on the initial pressure, as well as in case of high-voltage electric pulse consolidation of powder materials by spark plasma sintering and electrothermal explosion methods.

Pulse Plasma Sintering of NiAl-Al2O3 Composite Powder Produced by Mechanical Alloying with Contribution of Nanometric Al2O3 Powder.

NiAl-Al2O3 composites, fabricated from the prepared composite powders by mechanical alloying and then consolidated by pulse plasma sintering, were presented. The use of nanometric alumina powder for reinforcement of a synthetized intermetallic matrix was the innovative concept of this work. Moreover, this is the first reported attempt to use the Pulse Plasma Sintering (PPS) method to consolidate composite powder with the contribution of nanometric alumina powder. The composite powders consisting of the intermetallic phase NiAl and Al2O3 were prepared by mechanical alloying from powder mixtures containing Ni-50at.%Al with the contribution of 10 wt.% or 20 wt.% nanometric aluminum oxide. A nanocrystalline NiAl matrix was formed, with uniformly distributed Al2O3 inclusions as reinforcement. The PPS method successfully consolidated NiAl-Al2O3 composite powders with limited grain growth in the NiAl matrix. The appropriate sintering temperature for composite powder was selected based on analysis of the grain growth and hardness of Al2O3 subjected to PPS consolidation at various temperatures. As a result of these tests, sintering of the NiAl-Al2O3 powders was carried out at temperatures of 1200 °C, 1300 °C, and 1400 °C. The microstructure and properties of the initial powders, composite powders, and consolidated bulk composite materials were characterized by SEM, EDS, XRD, density, and hardness measurements. The hardness of the ultrafine-grained NiAl-Al2O3 composites obtained via PPS depends on the Al2O3 content in the composite, as well as the sintering temperature applied. The highest values of the hardness of the composites were obtained after sintering at the lowest temperature (1200 °C), reaching 7.2 ± 0.29 GPa and 8.4 ± 0.07 GPa for 10 wt.% Al2O3 and 20 wt.% Al2O3, respectively, and exceeding the hardness values reported in the literature. From a technological point of view, the possibility to use sintering temperatures as low as 1200 °C is crucial for the production of fully dense, ultrafine-grained composites with high hardness.

Properties of nickel-chromium alloy Kh20N80 sintered from electroerosive powders obtained in kerosene

The results of experimental studies of the composition, structure and properties of the Kh20N80 nickel-chromium alloy from a powder obtained by electroerosive dispersion in lighting kerosene are presented. It is shown that the method of spark plasma sintering of this powder can be used to obtain products with a surface with low porosity, high microhardness and a homogeneous favorable structure.

CREATION AND PROPERTIES OF CERAMICS FROM NICKEL OXIDE NANOPOWDER

By means of the method of the spark plasma sintering (SPS) on the basis of nanodimensional powder of nickel oxide (with an average particle size of about 100 nm), the fine-grained (of 250 – 500 nanometers approximately), dense (5.93 g/cm3), strong ceramics with the high microhardness Hv = 8.2 GPa, ultimate compressive strength ?B = 0.4 GPa and Young?s modulus of elasticity E = 140 GPa is created. The obtained ceramic sample was nickel oxide NiO (73-1519) with cubic structure, space group Fm3m (No. 225) and lattice size a = 4.168 ?.

BiVO4 Ceramic Photoanode with Enhanced Photoelectrochemical Stability.

Monoclinic bismuth vanadate (BiVO4) is an attractive material with which to fabricate photoanodes due to its suitable band structure and excellent photoelectrochemical (PEC) performance. However, the poor PEC stability originating from its severe photo-corrosion greatly restricts its practical applications. In this paper, pristine and Mo doped BiVO4 ceramics were prepared using the spark plasma sintering (SPS) method, and their photoelectrochemical properties as photoanodes were investigated. The as-prepared 1% Mo doped BiVO4 ceramic (Mo-BVO (C)) photoanode exhibited enhanced PEC stability compared to 1% Mo doped BiVO4 films on fluorine doped Tin Oxide (FTO) coated glass substrates (Mo-BVO). Mo-BVO (C) exhibited a photocurrent density of 0.54 mA/cm2 and remained stable for 10 h at 1.23 V vs. reversible hydrogen electrode (RHE), while the photocurrent density of the Mo-BVO decreased from 0.66 mA/cm2 to 0.11 mA/cm2 at 1.23 V vs. RHE in 4 h. The experimental results indicated that the enhanced PEC stability of the Mo-BVO (C) could be attributed to its higher crystallinity, which could effectively inhibit the dissociation of vanadium in BiVO4 during the PEC process. This work may illustrate a novel ceramic design for the improvement of the stability of BiVO4 photoanodes, and might provide a general strategy for the improvement of the PEC stability of metal oxide photoanodes.

Microstructure and Properties of TiB2 Composites Produced by Spark Plasma Sintering with the Addition of Ti5Si3.

Titanium diboride (TiB2) is a hard, refractory material, attractive for a number of applications, including wear-resistant machine parts and tools, but it is difficult to densify. The spark plasma sintering (SPS) method allows producing TiB2-based composites of high density with different sintering aids, among them titanium silicides. In this paper, Ti5Si3 is used as a sintering aid for the sintering of TiB2/10 wt % Ti5Si3 and TiB2/20 wt % Ti5Si3 composites at 1600 °C and 1700 °C for 10 min. The phase composition of the initial powders and produced composites was analyzed by the X-ray diffraction method using CuKα radiation. The microstructure was examined using scanning electron microscopy, accompanied by energy-dispersive spectroscopy (EDS). The hardness was determined using a diamond indenter of Vickers geometry loaded at 9.81 N. Friction–wear properties were tested in the dry sliding test in a ball-on-disc configuration, using WC as a counterpart material. The major phases present in the TiB2/Ti5Si3 composites were TiB2 and Ti5Si3. Traces of TiC were also identified. The hardness of the TiB2/Ti5Si3 composites was in the range of 1860–2056 HV1 and decreased with Ti5Si3 content, as well as the specific wear rate Wv. The coefficient of friction for the composites was in the range of 0.5–0.54, almost the same as for TiB2 sinters. The main mechanism of wear was abrasive.

Functional Gradient Heat-Resistant Materials Manufactured by Spark Plasma Sintering

The objects of the study were powder samples PV-NiCr16Al6Y and PV-Ni75Al23W, intended for the formation of a sublayer in heat-shielding coatings. The aim of this work is to develop and study a sublayer with a complexly organized structure of a functionally graded material of the superalloy-sublayer-ceramic system for operation under thermal cyclic loads and high-temperature gas corrosion. Experimental samples of binding materials for heat-protective coatings (HPC) were obtained by the method of spark plasma sintering (SPS) at T = 1050 °C / 15-30 MPa / 5 min. Methods of laser diffraction, X-ray structural analysis, optical and scanning electron microscopy, X-ray fluorescence spectroscopy, microdurometry were used to study powders and consolidated materials. It is shown that irregular powders contain individual particles of some components - in PV-NiCr16Al6Y powder these are particles of chromium and yttrium, in PV-Ni75Al23W - tungsten and chromium. Consolidated sublayers of such powders exhibit inhomogeneity and irregular porosity. To solve the problem of forming a homogeneous binder sublayer, mechanical alloying of the powders before sintering is proposed. It was found that MA increases the homogeneity of the structure, excludes local inclusions of unreacted particles, and increases the activation of consolidation. MA and subsequent sintering opens up wide possibilities for controlling the structure, including the porosity of the sublayers, and specifying various options for the HPC architecture. Experimental samples of HPC on an Inconel 625 substrate with a mechanically activated PV-Ni75Al23W sublayer and dioxides Zr/Y (YSZ) outer ceramics were obtained by the SPS method. A model of the architecture of a HPC made of a layered binder with different porosities is proposed.

Enhanced Mechanical Properties of SiCw/ SiCp-Reinforced Mg Composites Fabricated by Spark Plasma Sintering

This study aims to fabricate SiC whisker (w)/ particle (p)-reinforced magnesium (Mg) composites with enhanced mechanical properties using spark plasma sintering (SPS) methods. It has been confirmed that dispersing state of SiCw can be improved by addition of SiCp. However, due to presence of voids and cracks between the oxide layers, surrounding SiCw/p, and Mg matrix in the composites, SiCw with SiCp cannot contribute to enhance the bending strength of Mg matrix. This issue can be tackled by adding low melting point metals such as Sn into the composites to fill the defects in the composites.

Multiferroic properties and impedance spectrum of Ho3+ and Ti4+ co-doped BiFeO3 ceramics

Bi0.8Ho0.2Fe0.95Ti0.05O3 (BHFTO) nanoceramics with a grain size below 100 nm were prepared by spark plasma sintering (SPS) method, and their sintering process, microstructure, dielectric, and magnetic properties were studied. The analysis of microstructure suggests the formation of orthorhombic structure (space group, Pnma) in BHFTO nanoceramics with a homogeneous distribution in grain sizes. The defect types in BHFTO nanoceramics are distinguished, oxygen vacancies are dominant defects in BHFTO nanoceramics. BHFTO nanoceramics showed a high magnetization due to the broken of spin spiral structure in BiFeO3 system.

Investigation of the microhardness of the W-Ni-Fe powder alloy used for the restoration of machine parts

The paper presents the results of a study of the microhardness of the WNF-95 sintered electroerosive powder alloy. Powder alloy W-Ni-Fe95 was obtained by electroerosive dispersion of tungsten-containing waste in a kerosene medium. The resulting electroerosive powder alloy W-Ni-Fe 95was pressed in a vacuum chamber and sintered by the method of spark plasma sintering. The aim of this work was to study the microhardness of the WNF-95 sintered powder alloy obtained by the electroerosive dispersion of tungsten-containing waste in a kerosene medium. It has been established that the microhardness of samples sintered by the method of spark plasma sintering from particles of W-Ni-Fe 95alloy dispersed by electric erosion obtained in lighting kerosene is 2185.8 MPa and 2268.0 MPa, indicating their suitability for the manufacture of tungsten-nickel-iron alloys.

FGM Architecture with Heat-Resistant Properties

A composite laminated heat-resistant material was manufactured by the method of spark plasma sintering. The architecture of a bonding layer between a substrate made of a heat-resistant superalloy and a ceramic coating containing sublayers of the intermetallic NiAl and a mixture of NiAl with 15 or 30 wt. % zirconia (8YSZ) is proposed. In a layered composite, the microhardness and thermal conductivity change monotonically on going from the substrate to the outer ceramic. The coefficient of linear thermal expansion of the bonding layer is close to that for ceramics in the operating temperature range.

X-ray diffraction analysis of a sintered product made of electroerosive chromium-containing powder

This article presents the results of x-ray diffraction analysis of a sintered sample made of X13 alloy electroerosive materials obtained in butyl alcohol. It was found that in the sintered sample by the method of spark plasma sintering from alloy X13, the main phases are Fe, Cr, and FeNi3.

Study of the method of electric pulse plasma sintering of ceramic materials of the Primorsky krai with mechanoactivated additives

Study of the method of electric pulse plasma sintering of ceramic materials of the Primorsky krai with mechanoactivated additives

X-ray spectral microanalysis of W-Ni-Fe pseudoalloy obtained from electroerosive powders

The results of X-ray spectral microanalysis of W-Ni-Fe pseudo-alloy, obtained from electroerosive powders, are presented. Consolidation of the obtained electroerosive powders was carried out by the method of spark plasma sintering using the SPS 25-10 spark plasma sintering system. Using an EDAX energy-dispersive X-ray analyzer built into a Quanta 600 FEG scanning electron microscope, characteristic X-ray spectra were obtained at various points on the sample surface and along a transverse section. As a result of the study, it was found that on the surface of the investigated sintered sample, tungsten, nickel and iron are contained as the main elements, and oxygen, copper and chromium are also present in small amounts.

Investigation of the Microstructure of a Sintered Sample Obtained from Powder Steel X13

This article presents the results of a study of the microstructure of a sintered sample made of alloy X13 electroerosive materials obtained in butyl alcohol. It has been established that during the sintering of electroerosive materials made of alloy X13 by the method of spark plasma sintering, the main elements on the surface of the particles are Fe, Cr, Mn, and the particles have a generally regular spherical shape.

Reduced interlayer defects of diamond/copper composite doped with holmium (III) oxide

ABSTRACT The interlayer defects of diamond/copper (Cr) composite have been eliminated by adding holmium (III) oxide through Spark Plasma Sintering (SPS) method. The effects of Ho2O3 addition of diamond–copper interlayer on the microstructure and phase composition are investigated. The total density of states (DOS) and partial density of states (PDOS) are investigated by the first-principles calculations. It is revealed that the addition of Ho2O3 has a distinct modification effect on diamond–copper (Cr) interlayer. Obvious cracks around the diamond outer surface are hardly found, and the diamond particles are enfolded by the copper matrix. The Cr2C phase that beneficial to reduce interlayer defects and improve interlayer bonding was generated under the effect of adding Ho2O3. The thermal conductivity of diamond/copper (Cr-Ho2O3) is 686 W/(m·K). The possible reasons for doping Ho2O3 to eliminate interlayer defects and improve the thermal conductivity were discussed.

Enhancing mechanical properties of hydroxyapatite-reduced graphene oxide nanocomposites by increasing the spark plasma sintering temperature

In this study, the reduced graphene oxide (rGO)-Hydroxyapatite (HA) powders were first synthesized by a hydrothermal method. The amount of graphene in these powders was 1.5% by weight. Subsequently, these powders were consolidated at 900, 930, and 950 °C by spark plasma sintering (SPS) method, while the pressure applied in the process was 50 MPa. The sintered samples were characterized by X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and Vickers indentation methods. The results of this study showed that increasing the sintering temperature increased the relative density of the samples. Mechanical properties such as elastic modulus and hardness increased with increasing sintering temperature. The results of the microscopic analysis confirmed the presence of rGO sheets in the final nanocomposites. According to the findings of this study, considering the applied conditions, the best temperature for sintering was 950° C.

Boronizing of AISI 316L Stainless Steel Using Spark Plasma Sintering Technique

Austenitic stainless-steel has been widely used. Although it offers excellent corrosion resistance, processability, and nonmagnetic properties, it is inferior in terms of wear resistance and hardness. Therefore, the purpose of this study is to form iron boride on an austenitic stainless-steel surface using the spark plasma sintering (SPS) method and to evaluate its properties. The SPS method was utilized because the rapid heating involved in the process reduces the processing time. AISI 316L as a sample material was boronized for 3.6 ks at 1073 – 1273 K at applied pressures of 4 MPa and 8 MPa with a powder mixture of B4C and KBF4. The Vickers hardness profile results showed that the hardness of the untreated sample was ~ 200 HV whereas that of the boronized sample was ~ 2300 HV. The wear test profile showed that the wear resistance of the boronized sample was significantly improved. Moreover, according to elemental analyses, boron diffused from the sample surface to 200 μm and 60 μm when the applied pressure was 8 MPa and 4 MPa, respectively. This indicated that boron diffused to a greater depth when the applied pressure was increased.