Direct Selective Laser Sintering of Reaction Bonded Silicon Carbide

Three-dimensional reaction bonded silicon carbide (SiSiC or RBSC) parts have been produced by direct selective laser sintering (SLS). Unlike previously investigated processing routes, which make use of a sacrificial polymer binder to form green parts, the parts in this work are built by scanning subsequent layers composed of a mixture of silicon and silicon carbide powders. A fibre laser is used to selectively melt the silicon under an inert argon atmosphere, resulting in porous preforms of sufficient strength for further handling and processing. After impregnation with a graphite suspension and infiltration with liquid Si at 1450°C, highly dense reaction bonded silicon carbide parts are obtained.Mechanical Engineerin

Effect of surface finishing on tribological properties of ZrO2-based composites

Laboratory-made ZrO2-based composites with 40 vol. % WC, TiCN or TiN were tested in dry sliding contact with WC-6wt%Co cemented carbide using an ASTM G133 pin-on-flat configuration. Surface characterization included profilometric measurement, scanning electron microscopy, energy disperse X-ray analysis and X-ray diffraction. ZrO2-based composites with wire-EDM surface finish displayed higher friction coefficient and wear level compared to their ground equivalents. This finding was correlated to flexural strength measurements, revealing strong discrepancy between both surface finishes. ZrO2-WC composites exhibited superior tribological characteristics compared to the ZrO2-TiCN and ZrO2-TiN grades

Dry sliding friction and wear response of WC-Co hardmetal pairs in linearly reciprocating and rotating contact

This paper presents an experimental evaluation of friction and wear properties of WC-Co cemented carbides. A comparison is made between unlubricated rotating and linearly reciprocating pin-onplate sliding pairs. The plate specimens were WC-10wt%Co grades surface finished by polishing or sequential wire-EDM steps, whereas WC-6wt%Co pins were used as counter body. The tests were carried out at room temperature using a sliding speed of 0.30m/s and mean Hertzain contact pressures of 1.76 and 2.08 GPa, i.e., normal contact loads of 15N and 25N, respectively. The worn surfaces on plate samples were quantified in terms of 2–D wear profiles obtained by means of surface topography scanning equipment. Wear mechanisms such as polishing and abrasion were identified using optical microscopy. Inferior tribological characteristics for wire-EDM surface finish compared to polishing were found. Higher friction coefficient and wear levels were measured in unidirectional rotating sliding experiments compared to linearly reciprocating test conditions

In-situ measurements of high-temperature dielectric properties of municipal solid waste incinerator bottom ash

[EN] Microwave heating is a potential green technology demonstrating many advantages over conventional heating methods. Prior to designing an industrial microwave process, however, a fundamental knowledge of the dielectric properties of the material to be thermally treated is imperative, as these properties determine the response of the material to an applied electromagnetic field. In this study, the fundamental interactions between microwave energy and municipal solid waste incinerator (MSWI) bottom ash (BA) are investigated through in situ complex permittivity measurements. Using an enhanced version of the cavity perturbation method, the dielectric properties were determined from room temperature up to 1100 degrees C at a frequency close to the industrial 2.45 GHz. The results demonstrated that BA is a low-loss microwave absorber up to 320 degrees C, above which microwave flash pyrolysis of the organic matter abruptly enhances the dielectric loss of BA, resulting in a thermal runaway. The addition of water and graphite to BA induces a higher dielectric constant and loss factor. The evolution of the dielectric properties as a function of temperature is correlated to changes in the material as determined by Simultaneous Differential Scanning Calorimetry, Thermogravimetric Analysis and High Temperature X-ray Diffraction. The reported results form a baseline for the assessment of the MSWI BA response under microwave irradiation.This work was supported by the European Community's Horizon 2020 Programme under Grant Agreement No. 721185 (MSCA-ETN NEW-MINE). This publication reflects only the authors' view, exempting the Community from any liability. Project website: http://new-mine.eu/.Flesoura, G.; García-Baños, B.; Catalá Civera, JM.; Vleugels, J.; Pontikes, Y. (2019). In-situ measurements of high-temperature dielectric properties of municipal solid waste incinerator bottom ash. Ceramics International. 45(15):18751-18759. https://doi.org/10.1016/j.ceramint.2019.06.101S1875118759451

A new approach for the vitrification of municipal solid waste incinerator bottom ash by microwave irradiation

Encouraging the transition to a circular economy, the valorization of municipal solid waste incinerator (MSWI) bottom ash (BA) has received considerable attention in many processes. In the present work, flash microwave vitrification was effectively realized in a single mode cavity operating at 2.45 GHz within 1.5 min. The closed-loop process was evaluated in terms of energy and power input, treatment time and vitrified bottom ash (VBA) yield rate. The required minimum energy consumption was ∼3300 kJ/kg. By conducting thermo-electromagnetic multiphysics simulations, the heating mechanism of BA by microwave irradiation was underpinned. This relied on the generation of microwave-induced hot spots inside the material and high power density, in the order of 3 × 107 W/m3, that triggered the onset of BA melting at high heating rates. The inherent cold environment of the microwave cavity, due to the absence of any insulation material, in conjunction with the high silica content of BA promoted the glass forming ability of the melt. This allowed a natural fast cooling of the melt and VBA production, avoiding the cost and environmental impact accompanying conventional quenching. Preliminary characterization of the highly amorphous VBA product was performed and its exothermal heat flow after alkali activation revealed the potential incorporation in the binder of novel building materials

Tribological behavior of wire-EDM'ed ZrO2-composites and cemented carbides

Five ZrO2-based composites (ZrO2-WC, ZrO2-TiCN and ZrO2-TiN grades) and five WC-Co cemented carbide grades were machined by wire-EDM and tested on a linearly reciprocating sliding pin-on-flat tribometer PLINT TE77 in dry conditions against WC-6wt%Co pins. Measurement of friction coefficient and penetration depth due to wear was performed continuously. The results revealed a strong influence of the secondary phase, surface finish, chemical and mechanical properties on the tribological characteristics of the ZrO2-based composites and cemented carbides. WC10Co(Cr/V) displayed superior wear resistance compared to the other grades. The lowest coefficient of friction was encountered with ZrO2-WC

Data Mining and Social Media for promotion and marketing in the Aerospace Industry

Data mining and social media is an innovative platform for the aerospace industry to focus, promote and market the industry in the upcoming economy. Data mining techniques allow the industry to build a comprehensive system that helps to make intelligent management decisions in a formal system. On the other hand Social Media is used as a tool to ensure maximum return by entering a hybrid media landscape, one where the rapid growth of Social Media complements and enhances the efficiency of the industry. By using trend analysis this research would showcase benefits that the industry will achieve by increasing their profit margins and market competiveness. This research mainly focuses on supporting the aerospace industry to build trust among customers and meeting demand specifications by using data mining techniques and social media platform

On-line and post-mortem wear measurement of static counterpart in a ball-on-disk test

this paper presents an experimental evaluation of friction coefficient and wear of WC binderlessceramics. The tests were conducted at room temperature and atmospheric conditions according to theASTM G99-95a standard. Silicon carbide (SiC) balls were used as static counterpart. The tests wereperformed at a rotating sliding speed of 0.3 m/s and an initial mean Hertzian contact pressure of 1.9 GPa.The disk specimens were surface finished by grinding. On-line monitoring and post-mortem analysis withtwo independent techniques, i.e., surface profilometry and optical microscopy, were used to elucidate thetribological characteristics of the studied material. Results of the post-mortem measurements werecompared to a geometrical wear model for calculation of the volume of the worn cap of the ball. Thiscalculation appeared to be in good agreement with the on-line wear monitoring. The first 100 m of slidingwas identified as running-in period. Beyond a sliding distance of 100 m a steady stage in penetration depthwas reached, while a higher fluctuation in friction coefficient was observed, which could be attributed to theinteraction with wear particles and simultaneous formation and delamination of debris layer, polishing andabrasion

Fabrication, wear and performance of ceramic cutting tools

The ceramic cutting tool requirements for metal machining are reviewed, taking into account the trends in industry towards dry high-speed cutting and the need for tools with complex geometry. The emphasis will be on bulk materials rather than on coatings and most attention will be devoted to machining of iron-based alloys (steels). In the development of new tool materials, special attention should be given to the chemical matching of tool and workpiece material at elevated temperatures. The chemical compatibility of the tool-workpiece combination can be investigated by means of static interaction couples at elevated temperatures, which have been exposed for times long enough to be able to characterise the interaction layer. Complementary to the experimental investigation, the chemical compatibility of tool and workpiece materials can be predicted from thermodynamic equilibrium solubility calculations of tool materials in a selected workpiece material. Taking into account the mechanical properties needed, new ZrO2-based composites were defined based on the thermodynamically estimated chemical stability. The selection, development and proof testing of the new ZrO2-based composites is highlighted and their wear behaviour and performance in high speed dry turning of construction steel is compared with that of state-of-the-art cutting tool materials.status: publishe