WC Samples Research Articles

Influence of high temperature exposure on compressive strength and microstructure of ultra-high performance geopolymer concrete with waste glass and ceramic

This research evaluates the effect of high temperatures up to 800 °C on the compressive strength and microstructure of the developed ultra-high performance geopolymer concrete (UHPGC) containing waste glass (WG) and ceramic (WC). Fine aggregate was partially substituted with WG and WC in the range of 7.5–22.5% by vol. Samples were heated in the range of 200–800 °C at a heating rate of 5 °C/min for 1.5 h. The visual appearance, mass loss, residual compressive strength, and microscopic investigation of UHPGC mixtures were investigated. The outcomes of the experiments demonstrated that the residual strength of UHPGC containing WG varied from 98% to 97%, 59%–63%, and 27%–32% after being subjected to 300, 600, and 800 °C, respectively. While WC samples had residual strengths varying from 86% to 83%, 51%–45%, and 24%–18%, respectively. Therefore, compressive strength deteriorates more slowly with an increase in WG than WC. Microscopy experiments showed that WC pore structure expanded with temperature, notably above 600 °C, while WG had less pore structure and enhanced residual strength. Finally, the incorporation of WG is more effective in UHPGC thermal stability up to 800 °C than WC. Thermogravimetric analysis (TGA) results revealed that the mixtures containing 22.5% WG maintained about 95% of its weight, while the mixtures incorporating 22.5% WC lost 8% of their weight. It is concluded that WG could be implemented as an eco-friendly material with desirable properties at high temperatures.

Электроимпульсное (“искровое”) плазменное спекание ультрамелкозернистых керамик WC – Al2O3

The sintering mechanisms of WC – Al2O3 nanopowder compositions with different contents of aluminum oxide particles (1, 3, 5 wt.%) were investigated. Samples of WC – Al2O3 ceramics were produced by Spark Plasma Sintering method (SPS) in vacuum, by heating to a temperature of 1450 °C at a rate of 50 °C/min under uniaxial stress 70 MPa. Plasma-chemical nanopowders of tungsten monocarbide and submicron powders of aluminum oxide were used to make the ceramics. The density, microstructure, phase composition, microhardness (Hv) and fracture toughness (KIC) of the ceramics were investigated. It was shown that the use of the SPS method makes it possible to obtain WC-Al2O3 ceramics with good relative density (95.4-98.1%) and a homogeneous microstructure with ultrafine grain size (0.1 – 0.2 μm). By the method of the X-ray phase analysis, it was established that in the process of SPS of WC-Al2O3 ceramics the formation of an undesirable W2C phase takes place, leading to decrease in the fracture toughness KIC. To reduce the intensity of W2C particle formation, colloidal graphite (0.1, 0.2, 0.3 wt.%) was added to WC – Al2O3 ceramics. Using the Young-Cutler model and the model of diffusion resorption of pores it was shown that the main mechanism of SPS of WC – Al2O3 ceramics is grain boundary diffusion. It is shown that the introduction of graphite leads to a decrease in the activation energy of SPS of WC – Al2O3 ceramics, which is probably due to a decrease in the W2C particle content to 0.5 wt.%.

Microstructure evolution and enhanced mechanical properties of additively manufactured CrCoNi medium-entropy alloy composites

High-entropy alloys (HEAs) and medium-entropy alloys (MEAs) are regarded as promising advanced material with vast potential applications because of their many functional properties. However, the lower yield strength (YS) and wear resistance of as-cast face-centered cubic (FCC) phase HEAs/MEAs restricts their wide application in industry. In this study, the microstructure evolution, crystallographic orientation, tensile properties and wear resistance of CrCoNi metal matrix composites (MMCs) with different amounts of Mo and WC particles manufactured by directed energy deposition (DED) were systematically analyzed. Microstructure observation revealed that Mo segregated at the cellular boundaries and grain refinement occurred when WC particles were added, but the intensity of< 001 > crystallographic orientation along the build direction did not change significantly. The tensile results show that the YS and ultimate tensile strength (UTS) are increased by 56.18% and 35.45% respectively without significant decrease in ductility (from 46.92% to 42.51%) when 6.5 at% Mo and 2 wt% WC were added. Meanwhile, the wear resistance of Mo6.5 + 2 wt% WC samples are increased by 7.45 times compared with the CrCoNi matrix. These findings provide a new perspective for additive manufacturing (AM) of HEAs/MEAs MMCs with excellent strength-ductility combination and wear resistance.

Low-temperature corrosion behavior of laser cladding metal-based alloy coatings on EH40 high-strength steel for icebreaker

Abstract In this paper, four kinds of coatings Ni + 30% WC, Ni + 15% WC, Ni, and Co are prepared on EH40 steel by laser cladding technology. Electrochemical experiment tests at a simulating low-temperature (–40°C) environment in 0.5 mol·L−1 hydrochloric acid (HCl) solution and 3.5 wt% NaCl solution were conducted, and the polarization curve and electrochemical impedance spectroscopy (EIS) impedance spectrum were obtained. The results show that the Ni + 15% WC coating has the smallest corrosion current and 0.5 mol·L−1 HCl solution and 3.5 wt% NaCl solution have the maximum polarization resistance and impedance arc. Coatings will be treated in a 0.5 mol·L−1 HCl solution and 3.5 wt% NaCl solution at –40°C immersion for 30 days; finally, X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) were used for test passivation films of Ni + 15% WC samples and sample surface morphology after corrosion. XPS results show that Fe, Mo, and Ni elements can form metal oxides in the 0.5 mol·L−1 HCl solution, and Cr, Fe, Mo, Ni, and W elements can form metal oxides in the 3.5 wt% NaCl solution. SEM results display that relatively severe corrosion appeared on the substrate near tungsten carbide in a 0.5 mol·L−1 HCl solution, and coating will be corroded form inside of the coating owing to the corrosive solution will penetrate the substrate. In 3.5 wt% NaCl solution, severe corrosion of the substrate has not been observed; however, the binding part has been obviously corroded.

Microstructural evolution and mechanical characterization of a WC-reinforced CoCrFeNi HEA matrix composite

High entropy alloys (HEAs) are a relatively new class of material that have shown the potential to exhibit excellent combinations of mechanical properties. Various microstructural modifications have been explored to further enhance their mechanical properties for use in demanding structural applications. The main focus of the present work is an investigation of the effect of adding varying amounts of hard ceramic material (WC) to a tough HEA matrix (CoCrFeNi) by arc melting under an argon atmosphere, including microstructural changes, and evaluation of the WC additions on mechanical properties. X-ray diffraction analysis of the HEA-WC composites showed the presence of both fcc and carbide phases. Scanning electron microscope investigations, including energy dispersive spectroscopy, reveal that chromium diffuses from the matrix and interacts with WC to form an alloyed carbide phase. The amount of alloyed carbide was found to increase with increasing amount of WC addition to the HEA matrix. Mechanical characterization revealed that hardness and yield strength of the HEA-WC composites increase with increasing amount of the carbide phase in the matrix. The hardness of HEA-20wt.% WC sample was found to be as high as 3.3 times (593 HV) the hardness of the base HEA (180 HV), while the yield strength increased from 278 MPa for the base HEA to 1098 MPa for the CoCrFeNi-20 wt.% WC composite. The investigated composites also showed excellent values of ductility (~ 50% strain for CoCrFeNi-10 wt% WC and ~ 20% strain for CoCrFeNi-20 wt% WC). It is therefore believed that ceramic-reinforced high entropy matrix composites have the potential to provide outstanding combinations of mechanical properties for demanding structural applications.

High pressure synthesis of tungsten carbide–cubic boron nitride (WC–cBN) composites: Effect of thermodynamic condition and cBN volume fraction on their microstructure and properties

Tungsten carbide (WC) with different amounts of Cubic boron nitride (cBN) were synthesized by High Pressure-High Temperature (HPHT) method. The mapping correlation between thermodynamic condition, cBN addition, and microstructure, mechanical properties of WC–cBN composites was established and analyzed by response surface methodology. The main factors affecting the properties of composites were identified by ANOVA. The optimum thermodynamic condition was calculated. It was found that a minor phase transformation of cBN into the low-hardness hBN occurred at a temperature of 1300 °C and intensified at 1500 °C. The homogeneously dispersed cBN particles in the WC matrix promoted an improvement of hardness and fracture toughness, but the phase transition of cBN and its truss effect can dramatically reduce the mechanical properties. The Vickers hardness and fracture toughness of the well-sintered WC-cBN bulks reached a high value of 34 GPa and 13.6 MPa·m1/2, which are improved by 17% and 52% respectively compared with the pure WC samples sintered under similar high-pressure level.

Sliding wear and friction behaviour of WC‐stainless steel and WC–Co composites

AbstractThe sliding wear and friction behaviour of new developed WC‐stainless steel composites without and with carbon addition were evaluated using a linearly reciprocating sliding tribometer under ball‐on‐flat configuration, sliding against an alumina ball under unlubricated conditions. The wear of both, discs and ball were measured for different applied loads, sliding distances and frequencies. Worn surfaces were investigated by using microscopy and topography techniques. Comparative experiments were performed using flat samples of a conventional WC–Co composite. It was found that the WC–Co grade displayed an undoubtedly better sliding wear resistance and lower coefficient of friction if compared with the newly produced WC‐SS composites.

Prevalence of Anemia, Iron Deficiency during the Second Trimester of Gestation in Pregnant Women: A Comparative Study of Walled and New Lahore City Population

Background: Anemia during pregnancy is common worldwide, and it is also reported in Lahore, Pakistan, but it is not well documented in women residing in the Walled City of Lahore (WC). The study was designed to compare the pregnant female population of walled and new Lahore (NC) city for the prevalence of anemia and iron deficiency.&#x0D; Methods: All the females were within the second trimester of pregnancy with World Health Organization (WHO) criteria of age between 18-45 years. 446 venous blood samples were drawn, out of which 180 belong to WC and 266 to NC. After informed consent, demographic information, including age, gravidity, education, and socioeconomic status, was collected. A complete blood count test was performed to get results for hemoglobin, MCV, and MCH. Total iron-binding capacity, ferritin, and hepcidin levels were checked on ELISA 96-wells plates.&#x0D; Results: The prevalence of anemia in WC samples is 58.3%, and in NC samples, it is 42.4%. A decrease in hepcidin is significantly (p &lt; 0.05) associated with age and gravidity in both populations.&#x0D; Conclusion: It is concluded that anemia control programs should focus on WC women with extra efforts as anemia and iron deficiency are more prevalent. Making intelligent and focused efforts about this public health worry, Pakistan may succeed in achieving Sustainable Development Goals 2025 about eradicating anemia.

A novel WC\u2013W2C composite synthesis by arc plasma melt cast technique: microstructural and mechanical studies

WC–W2C composites of three different compositions have been synthesized from mixture of WC + W (0, 5 and 16 wt% W) by thermal arc plasma melt-cast technique. Various grown phases observed in the composites consisting of major phases of WC and W2C and minor phases of unbound C (graphite) and tungsten (W) were confirmed by X-ray diffraction, selected area electron diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared studies. Transmission electron microscopy and field emission scanning electron microscopy show polycrystalline nature of composites. Energy dispersive spectroscopy (of X-ray) infers the absence of any impurity in the composite. Almost porous free nature of composites were observed from X-ray micro computed tomography and BET analysis studies. WC–W2C composite (16 wt% W) shows 25% and 21% higher micro hardness (2535 VHN) and Young’s modulus (625 GPa) values than that of pure melt cast WC sample.

Transcriptomics analysis of the metabolic mechanisms of iron reduction induced by sulfate reduction mediated by sulfate-reducing bacteria.

Sulfate-reducing bacteria (SRB) play an important role in sulfur, iron and carbon cycling. The majority of studies have illustrated the role of SRB in biogeochemical cycling in pure cultures. In this study, we established three SRB enrichment cultures (designated HL, NB and WC) from different paddy soils and conducted a transcriptomic analysis of their metabolic characteristics under sulfate and sulfate-free conditions. In the HL cultures, there was no sulfate consumption but ferrihydrite was reduced. This indicated that bacteria in the HL samples can reduce ferrihydrite and preferentially utilize ferrihydrite as the electron acceptor in the absence of both ferrihydrite and sulfate. Sulfate consumption was equal in the NB and the WC cultures, although more ferrihydrite was reduced in the NB cultures. Transcriptomics analysis showed that (i) upregulation of O-acetylserine sulfhydrylase gene expression indicating sulfate assimilation in the WC samples; (ii) the energy conservation trithionate pathway is commonly employed by SRB and (iii) sulfate not only enhanced iron reduction by its conversion to sulfide but also promoted enzymatic electron transfer via c-type cytochromes.

Comparing the performance of different extruders in the Robocasting of biopolymer-nanoparticle composites towards the fabrication of complex geometries of porous Tungsten Carbide

Porous tungsten carbide (WC) is a material that combines a high strength to weight ratio and electroconductivity, which makes it a candidate for the creation of lightweight structures with the application as structural energy components, or SECs. However, machining complex geometries out of porous WC can be challenging and can lead to a significant waste of material. Here we present the use of robocasting to print geometries using paste featuring a biopolymer and tungsten oxide nanoparticles. Once printed, these geometries can be heat treated in an inert environment to derive porous WC. The benefit of using an additive manufacturing approach towards the production of porous WC is the possibility of producing complex geometric samples for industrial applications that cannot be created through traditional machining techniques. While the robocasting approach we reported before succeeded in producing WC samples, such a process led to the poor print quality of the desired geometries due to inconsistent extrusion flow rate throughout the printing process. The consistent flow generated by the new robocasting system proposed here has resulted in reduced layer irregularities, leading to the improved print quality of the WC precursor when compared to our previous approach. The production of consistent geometries will now allow for conclusive experimentation on the drying and carbonization processes and serves as a robust step forward to unlocking the potential of manufacturing porous WC SECs using robocasting.

Effect of vegetable fat on the texture, colour and sensory properties of Macedonian white brined cheese

This study aimed to investigate the influence of substitution of milk fat with palm fat on the composition, yield and technological quality of White cheese, a Macedonian traditional cheese. In this study, full-fat white brined cheese was used as a control sample (WC), while experimental cheeses were prepared from cow milk with vegetable fat (WV) addition and low-fat cheese (WL), respectively. The cheeses have been analysed for physicochemical (acidity, pH, fat, fat acidity, protein), instrumental texture and colour properties (L, a, b) as well as the sensory properties after 1, 20 and 60 days. WV cheeses showed a significantly (P&lt;0.05) lower degree of pH and higher titratable acidity than the WC and WL cheese samples. Cheese that contained vegetable fat showed lower degrees of lipolysis, as assessed by the acid-degree value and received significantly (P&lt;0.05) better appearance, highest hardness value (5226.98 N) and cheese yield scores compared to other samples.

W-ZrC composites prepared by reactive melt infiltration of Zr2Cu alloy into binder jet 3D printed WC preforms

W-ZrC composites were successfully prepared by reactive melt infiltration (RMI) of stoichiometric and excess amounts of Zr2Cu into sintered and un-sintered WC preforms made from binder jet 3D printing. The focus of this work was to study the conversion of reactant powders and liquid infiltrant with varying preform density and infiltrant amount by controlling the processing time to reach high conversion yield while understanding the phase composition, microstructure, and hardness. To investigate the effect of time, the reactive melt infiltration was conducted at 1400 °C for 2, 4 and 8 h in a furnace with 96% Ar - 4% H2 gas atmosphere. The increase in reaction time from 2 to 8 h increased the W and W2C phase contents and decreased the ZrC phase content when using sintered WC preforms. Samples prepared from un-sintered WC preforms exhibited improved reactive melt infiltration compared to sintered samples, and there was no detectable W2C phase and nearly full consumption of WC. Similar to sintered WC samples, the content of W and ZrC phases increased with the increase in time from 2 to 8 h. The interfaces and phases at reaction interfaces were investigated using electron diffraction analysis and S/TEM-EDS to understand material stability; the phases were identified and consistent with XRD analysis. Additionally, there was no Cu present at the interfaces. Increasing the amount of infiltrant led to better reactive melt infiltration. In general, the hardness increased with reaction time and the highest Vickers hardness was found in the W-ZrC sample formed from sintered WC reacted with excess Zr2Cu. This research addresses the critical comparison of sintering and RMI time and shows that by using un-sintered samples for 8 h we are able to achieve W-ZrC composites with fewer undesired phases.

X-ray diffraction layer-by-layer analysis of tungsten carbide-based hard alloys

Improvement of the physical and mechanical properties of hard alloys based on WC – Co widely used in manufacturing of structural and tool products nowadays results from the use of novel technologies providing formation of a homogeneous high-density structures. Slight deviations of the carbon content from the equilibrium state lead to the formation of brittle η-phases (in particular, Co3W3C) and, accordingly, to deterioration of the mechanical properties of the product. We present the results of studying the homogeneity of the phase composition of the samples of hard alloys WC + 10% Co, obtained using advanced technologies of plasma-chemical synthesis and spark plasma sintering (SPS). The layer-by-layer X-ray phase analysis revealed the heterogeneity of the phase composition in depth: the brittle η-phase (Co3W3C) appears at a depth of ≥100 μm and reaches a constant value of 18 ± 1 wt.% at &gt;200 μm, which indirectly confirms the hypothesis of carbon diffusion from graphite punches contacting with the surface of sintered samples and makes it possible to expand the range of parameters affecting the process of spark plasma sintering.

Fatigue Life Enhancement of Titanium Alloy by the Development of Nano/Micron Surface Layer Using Laser Peening.

Ti-15V-3Cr-3Al-3Sn (Ti-15-3) is a metastable beta alloy which is considered to be a potential alternative for Ti-6Al-4V alpha+beta alloy for aerospace applications, especially for sheet products. This paper describes the work carried out to enhance the fatigue life of Ti-15-3 in an economical way by means of laser peening without coating (LPwC) using Nd:YAG laser operating at a power density of 5 GW cm-2. In order to have a sufficient bulk hardness and high compressive stresses on the surface, as-received beta solution treated (ST) Ti-15-3 was subjected to aging (520 °C/10 h/Air-cooled) and then to LPwC. Laser peening induced a notable increase in Ra (arithmetic mean roughness), which was measured using MAHR GD-120 profilometer. The Electron Back Scatter Diffraction (EBSD) analysis of the aged sample (STA) revealed a significant increase in the alpha precipitation (20 vol%), and this led to a substantial increase in the hardness (~40%) and UTS (~50%). In addition to this, peening of aged (STA+LPwC) sample resulted in a considerable increase (~12%) in near-surface microhardness and compressive residual stress (maximum stress of -195 MPa at a depth of 150 μm). This increase in compressive stress and microhardness led to an enhancement in the fatigue life of the STA+LPwC sample by 210% when compared to STA sample. In spite of high surface roughness induced by the LPwC, fractography studies revealed that crack initiation was independent of surface roughness.

A comparative study on the high temperature dry sliding wear behavior of TiN and AlTiN/TiSiN coatings fabricated by PVD technique

PurposeThis study aims to investigate the high-temperature wear behavior of the TiN- and AlTiN/TiSiN-coated WC materials.Design/methodology/approachThe coating process was carried out using the physical vapor deposition (PVD) method. Wear tests were performed by a ball-on-disc wear device with a high-temperature wear module. In microstructural investigation of the materials, it was benefited from traditional characterization methods such as, SEM, EDX analysis and microhardness measurement.FindingsThe best wear performance was obtained with AlTiN/TiSiN-coated WC materials at all loads and temperatures, followed by TiN-coated and uncoated WC samples. An important wear was not observed on the samples tested at room temperature tests. It was found that the temperature increase is an effective parameter on the decrease of the wear resistance of the samples. In addition, it was seen that the increasing load and temperature change the wear mechanism on the uncoated WC sample. The wear mechanisms observed at high temperatures were delamination and oxidation for the WC, fatigue for AlTiN/TiSiN-coated WC and micro-scratch and micro-spalling for TiN-coated WC.Originality/valueThe results of the experimental studies demonstrated that hard coatings improving wear resistance of WC.

Study effects on diamond concentration of CuSnFeNi/diamond composite on grinding WC

There are still some challenges to use metal matrix composites reinforced with diamond particles in grinding field because it is difficult to find a suitable metal matrix to balance the mechanical properties and grinding performance. In order to solve this problem, CuSnFeSn/diamond composites were fabricated by introducing hybrid microwave sintering with diamond concentration ranging from 40 to 70%. The microstructure, physical and mechanical properties, and critical grinding performance were investigated. Best balance of mechanical properties and grinding surface roughness occurred when the diamond concentration is 60%. It holds a hardness of 98.5 ± 0.5HRB, a flexural strength of 266.98 ± 15.6 MPa, an elastic modulus 46.62 ± 8.48GPa, and WC sample surface roughness Ra14.92 ± 2.92 nm. The grinding experiment results reveal that there are three wear modes in the processing, which are adhesive wear, plastic deformation, and sliding friction.

On the Interaction of the Cobalt Melt with Polycrystalline Tungsten Monocarbide

The interaction of the cobalt melt with hot-pressed and synthesized polycrystalline WC samples was studied. It is shown that the polycrystalline WC-mesoelements are promising for the development of WC–Co mesostructural hard alloys produced by liquid-phase sintering.

Development of novel methods to predict the strength properties of thermally treated sandstone using statistical and soft-computing approach

The knowledge of thermally modified strength properties is crucial in processes such as underground coal gasification, disposal of radioactive wastes in deep geological reservoirs and restoration of fire-damaged structures. However, due to the unavailability of dedicated laboratory equipment, scientists and engineers need to go across various laboratory facilities for testing their desired sample. Further, it delays the process and increases the cost of the project. Since there is a lack of empirical equations that can provide the strength of a thermally modified rock from the strength at room temperature, new predictive models have been developed using multivariate regression analysis (MVRA), artificial neural network and adaptive neuro-fuzzy inference system (ANFIS), to predict the uniaxial compressive strength (UCS) and tensile strength (TS) of both uncooled (NC) and heat-treated (WC) samples of a fine-grained Indian sandstone that has been widely used as a major building material in most of the Indian monuments. The UCS and TS of NC and WC samples have been predicted from the physical properties, viz. temperature (T), density (D), porosity (P), thermal expansion coefficients (EL and EV) and ultrasonic wave velocities (VP and VS). The performance and prediction efficiency of the models have been compared on the basis of performance indices, namely the correlation coefficient (R2), the mean absolute percentage error, the root mean square error and the variance account for. Based on the comparative study, it was concluded that ANFIS provides a relatively closer estimation as compared to MVRA.

Under-vine Management Impacts Soil Properties and Leachate Composition in a New York State Vineyard

Four under-vine management treatments were established in 2011 in a Vitis vinifera L. ‘Cabernet Franc’ vineyard in the Finger Lakes region of New York: cultivation (CULT), native vegetation (NV), white clover Trifolium repens L. (WC), and glyphosate herbicide (GLY) as the control. Previously installed drainage lysimeters were used to monitor nutrient and pesticide concentrations in leachate water samples. Differences in the physical structure of soils among treatments were only observed in the 4th year of the study when the top 6 cm of CULT soils had greater bulk density than the other treatments, and less porosity and available water capacity than WC soils. WC soils had 17% greater organic matter than CULT soils, and 46% greater aggregate stability than GLY soils. Soil microbial respiration was generally greater in NV and WC treatments than GLY and CULT. Dissolved organic carbon (DOC) leachate concentrations were greater in GLY and CULT compared with NV and WC, having annual mean DOC leachate concentrations as much as 36% greater than the cover crop samples. Mean annual total nitrogen (TN) leachate concentrations of CULT and NV were less than GLY and WC samples by as much as 86%. In 2012, GLY soils leached greater concentrations of imidacloprid insecticide and more imidacloprid metabolites than the other three treatments, with the proportion of samples testing positive for measurable concentrations of imidacloprid or imidacloprid metabolites at least five times greater in GLY than the other treatments. Cumulatively, these factors demonstrate the potential of under-vine cover crops to maintain soil quality and decrease the leaching of nutrients and agrochemicals in vineyards in comparison with conventional practices.