214 research outputs found

    Development of plasma-sprayed molybdenum carbide-based anode layers with various metal oxides for SOFC.

    Get PDF
    Air plasma-sprayed (APS) coatings provide an ability to deposit a range of novel fuel cell materials at competitive costs. This work develops three separate types of composite anodes (Mo-Mo2C/Al2O3, Mo-Mo2C/ZrO2, Mo-Mo2C/TiO2) using a combination of APS process parameters on HastelloyŸX for application in intermediate temperature proton-conducting solid oxide fuel cells. Commercially available carbide of molybdenum powder catalyst (Mo-Mo2C) and three metal oxides (Al2O3, ZrO2, TiO2) was used to prepare three separate composite feedstock powders to fabricate three different anodes. Each of the modified composition anode feedstock powders included a stoichiometric weight ratio of 0.8:0.2. The coatings were characterized by scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction, nanoindentation, and conductivity. We report herein that three optimized anode layers of thicknesses between 200 and 300”m and porosity as high as 20% for Mo-Mo2C/Al2O3 (250-”m thick) and Mo-Mo2C/TiO2 (300”m thick) and 17% for Mo-Mo2C/ZrO2 (220-”m thick), controllable by a selection of the APS process parameters with no addition of sacrificial pore-forming material. The nanohardness results indicate the upper layers of the coatings have higher values than the subsurface layers in coatings with some effect of the deposition on the substrate. Mo-Mo2C/ZrO2 shows high electrical conductivity

    Damage Tolerance of Thermally Sprayed Oxide Coatings

    Get PDF
    Termisesti ruiskutettuja keraamipinnoitteita kĂ€ytetÀÀn useissa sovelluksissa eri teollisuudenaloilla, kuten paperi- ja prosessiteollisuudessa, avaruus- ja ilmailuteollisuudessa, sekĂ€ energiantuotannossa. Pinnoitteille asetetut vaatimukset vaihtelevat kulumisen ja korroosion kestosta funktionaalisiin ominaisuuksiin, kuten alhaiseen pintaenergiaan tai lĂ€mmönjohtavuuteen. Oksidipinnoitteet, kuten yttriastabiloitu zirkoniumoksidi, alumiinioksidi, titaanioksidi ja kromioksidi muodostetaan yleisesti termisen ruiskutuksen prosesseilla kĂ€yttĂ€en atmosfÀÀristĂ€ plasmaa, suurnopeusliekkiruiskutusta tai perinteistĂ€ liekkiruiskutusta. Oksidipinnoitteiden suurin varjopuoli on niiden alttius katastrofaaliseen murtumiseen yhtĂ€kkisestĂ€, odottamattomasta iskusta johtuen. TĂ€mĂ€nkaltaisten iskujen mahdollisuus on jatkuvasti lĂ€snĂ€ useimmissa sovelluksissa, missĂ€ keraamisia pinnoitteita kĂ€ytetÀÀn, minkĂ€ vuoksi aihe herĂ€ttÀÀ kiinnostusta laajassa skaalassa teollisuuden aloja. LisĂ€ksi tĂ€mĂ€ pinnoitteiden ominaisuus — tĂ€ssĂ€ työssĂ€ nimetty vauriosietoisuudeksi — rajaa mahdollisten sovelluskohteiden mÀÀrÀÀ. TĂ€mĂ€n vuoksi pienikin parannus vauriosietoisuudessa voi avata ovia uusille teknologioille. Useita keinoja keraamipinnoitteiden vauriosietoisuuden parantamiseksi on kokeiltu, kuten metallin lisĂ€ystĂ€ pinnoitteeseen, oksidisekoituksia ja nanorakenteisia pinnoitteita, mutta toistaiseksi parannukset suorituskyvyssĂ€ ovat olleet varsin nimellisiĂ€, tai ovat heikentĂ€neet pinnoitteen muita hyödyllisiĂ€ ominaisuuksia. LisĂ€ksi vauriosietoisuuden mittaaminen tarkasti ja toistettavasti on haastavaa. Nykymenetelmiin kuuluu laboratoriomittakaavan kokeet, jotka antavat tietoa materiaalin ja pinnoitteen luonteesta, sekĂ€ sovelluspainotteiset kokeet, joista saatu tieto ei ole laajasti hyödynnettĂ€vissĂ€ muissa ympĂ€ristöissĂ€. TĂ€mĂ€n tutkimuksen pÀÀpaino oli arvioida eri menetelmiĂ€ termisesti ruiskutettujen keraamipinnoitteiden vauriosietoisuuden mittaamiseksi. Vauriosietoisuus jaettiin kahteen selkeĂ€sti toisistaan eroavaan ominaisuuteen: sĂ€rön etenemisen vastustuskykyyn ja matalaenergisten iskujen vastustuskykyyn. NĂ€istĂ€ edellinen on lĂ€hellĂ€ murtositkeyden mÀÀritelmÀÀ, mutta tĂ€htÀÀ tuottamaan laajemmin sovellettavia tuloksia. SĂ€rön etenemisen vastustuskyvyn mittausmenetelmiin luetaan nelipistetaivutus akustisella emissiolla instrumentoituna ja suuren energia iskut sĂ€rön polun tutkimisella. NĂ€mĂ€ menetelmĂ€t antavat tietoa mikrorakenteen vaikutuksesta pinnoitteen sitkeyteen. LamellienvĂ€linen koheesio paljastui sitkeyden kannalta heikoimmaksi lenkiksi, sillĂ€ heikko rajapinta luo helpoimman etenemisreitin sĂ€rölle. Edelleen kokeet paljastivat, ettĂ€ tiiviimmĂ€t HVOF-pinnoitteet kĂ€yttĂ€ytyivĂ€t hauraammin kuin plasmaruiskutetut vastinparinsa, sillĂ€ niissĂ€ ei ollut esisĂ€röytyneitĂ€ alueita, jotka voisivat vapauttaa pinnoitteeseen muodostuneita jĂ€nnitystiloja. Matalaenergisten iskujen vastustuskyky on hieman enemmĂ€n sovelluslĂ€htöinen tĂ€hdĂ€ten mukailemaan iskumaista vauriota tosielĂ€mĂ€n tilanteissa. Sen mittausmenetelmiin taas luetaan vĂ€syttĂ€minen mikrokoon iskuilla, joissa pieni painin iskeytyy pintaan toistuvasti korkealla taajuudella, sekĂ€ kavitaatioeroosio, jossa valtava mÀÀrĂ€ luhistuvista kuplista johtuvia iskeymiĂ€ tuottavat tilastollisen lĂ€hestymistavan mikrometriluokan pinnoitteen koheesion mittaamiseen. NĂ€iden testien tulokset korreloivat hyvin vauriosietoisuuden kĂ€sitteen kanssa, sillĂ€ ne mittasivat pinnoitteen ominaisuuksia yleisemmĂ€llĂ€ tasolla. Koska nĂ€mĂ€ mittaustavat hyödyntĂ€vĂ€t pieniĂ€ iskuja, pinnoitteen kovuus oli vauriosietoisuuden kannalta mÀÀrÀÀvĂ€ tekijĂ€, kunnes iskujen energia ylitti tietyn raja-arvon. TĂ€tĂ€ rajaa suurempienergiset iskut johtivat joko pinnoitteen katastrofaaliseen vaurioitumiseen tai vaiheittaiseen vaurion etenemiseen. NĂ€istĂ€ jĂ€lkimmĂ€inen on vahvasti suositumpi, sillĂ€ silloin tosielĂ€mĂ€n tilanteissa jÀÀ aikaa reagoida ennen komponentin tuhoutumista. Toissijainen painopiste oli parannetun vauriosietoisuuden keraamipinnoitteiden valmistaminen uusia ruiskutusprosesseja kĂ€yttĂ€en. TĂ€mĂ€n toteamiseksi kĂ€ytetÀÀn ensimmĂ€isessĂ€ vaiheessa arvioituja mittausmenetelmiĂ€. KĂ€ytetyt ruiskutusmenetelmĂ€t olivat suspensiosuurnopeusliekkiruiskutus ja nestemĂ€isen prekursorin ja jauheen syöttĂ€minen samanaikaisesti nk. hybridisuurnopeusliekkiruiskutuksessa. Suspensioruiskutetut kromioksidipinnoitteet osoittivat parannuksia vauriosietoisuudessa sĂ€ilyttĂ€en tai parantaen kulumisenkestoaan ja kovuuttaan. Alumiinioksidijauheen ja zirkoniumasetaattiliuoksen hybridiruiskutus paljasti tarpeen ruiskutusprosessin lisĂ€optimoinnille, sillĂ€ sulamattomat, prekursorista perĂ€isin olevat nanopartikkeliagglomeraatit heikensivĂ€t pinnoiterakennetta koheesion parantamisen sijaan. TĂ€stĂ€ huolimatta, pinnoitteen saumattoman rÀÀtĂ€löinnin lupaava potentiaali kannustaa tutkimaan myös hybridiruiskutusta tulevaisuudessa.Thermally sprayed ceramic coatings are utilized in various applications in industries, such as paper- and process, aerospace and energy production. The requirements for the coatings vary from wear resistance and chemical stability to functional properties, such as low surface energy or thermal conductivity. Oxide coatings, such as yttriastabilized zirconium oxide, aluminum oxide, titanium oxide and chromium oxide are commonly deposited by thermal spray processes using an atmospheric plasma, a high-velocity oxy-fuel or a flame spray torch. The biggest drawback of the oxide coatings is their susceptibility to catastrophic failure from sudden, unexpected impacts, consequently leading to the functional failure of the component. The possibility of such impacts is omnipresent in most applications where ceramic coatings are used, which makes the topic attractive to a wide range of industries. This property of the coatings — named damage tolerance for the purposes of this thesis — additionally limits the number of possible applications. Therefore, any improvement in damage tolerance could open doors to various new technologies. Multiple workarounds have been attempted in improving the damage tolerance of ceramic coatings, such as metallic additions, oxide mixtures and nanostructured coatings, but so far increases in performance have been modest or have deteriorated other beneficial functions of the coating. Furthermore, there lies a challenge in accurate and repeatable measurement of the damage tolerance. Current methodology includes testing in laboratory scale, giving information on the nature of the material and coating, and application-based testing, where the obtained information is not widely applicable in other conditions. In this study, the primary focus was to evaluate different methods of measuring the damage tolerance of thermally sprayed ceramic coatings. Damage tolerance was divided in two distinguishable properties: crack propagation resistance and resistance to low-energy impacts. The former is akin to fracture toughness, but aims to give a more transferable result. Measurement methods of crack propagation resistance evaluated include four-point bending with acoustic emission instrumentation and high-energy impacts from spherical projectiles with crack path tracing. These methods provided insights into the effect of microstructure on the toughness of the coating. Interlamellar cohesion was shown to be the weakest link of toughness in that the weak interfaces provide the path of least resistance for crack propagation. Additionally, denser HVOF coatings proved more brittle than their plasma-sprayed counterparts as they did not have stress-relieving zones from pre-cracked areas. The low-energy impact approach is slightly more application-oriented, aiming to emulate impact damage conditions in real-life environments. The methods used to measure it are micro-impact fatigue, where a small indenter is repeatedly impacted on the surface with high frequency, and cavitation erosion, where a vast number of impacts from collapsing bubbles create a statistical approach to measuring coating cohesion in the micrometer scale. The results of these tests correlated well with the concept of damage-tolerance as they measured the properties of the coating in a more general level. Since these methods rely on small impacts, hardness of the coating was a determining factor of damage-tolerance until the energy of the impact rose past a coating-specific threshold. Above this value, the coatings either failed catastrophically, or showed a more gradual failure propagation. The latter of these behaviors is highly preferred, as it gives time to react before the component fails in real conditions. The secondary focus was to create ceramic coatings with increased damage tolerance through novel spray processes, as measured by the screened testing methods. The spray methods were suspension HVOF-spraying and solution-precursor -powder hybrid HVOF spraying. The suspension sprayed Cr2O3-coatings provided improvements in damage tolerance with similar or improved levels of wear resistance and hardness. The hybrid-spraying of Al2O3 powder and a zirconium acetate based precursor proved to still require further optimization of the spray process, as unmolten agglomerates of precursor-derived nanoparticles rather weakened the coating, instead of improving the cohesion. Nonetheless, promising potential is foreseen for the hybrid-spraying in the future due to its ability to tailor the coating composition rather seamlessly

    Experiment Evaluation on the Porosity of Plasma Coating from Ceramic Al2O3 – TiO2 Using the Metallography

    Get PDF
    Background: The objective of this paper is an experimental investigation of the metallographic porosity of plasma coating using standard materials from the ceramic system Al2O3-TiO2 on the substrate of steel SS400 at laboratory scale Lab at the Research Institute of Mechanical Engineering. Contribution: The main contribution of the research is the evaluation of the porosity of the coating under the influence of the main technological parameters since the porosity plays a significant role in the performance of the working surface using the built-in Image Pro-Analyzer software in the Axiovert 25 MAT microscope. Method: The spraying material is Al2O3-TiO2 powder. The input parameters are: spraying distance (Lp; current of plasma stream (Ip); powder feed flow (Gp and spraying rate (Vp). Results: The findings show that the average porosity of the Al2O3-TiO2 plasma coating is inversely decreasing in the increasing direction of the distance: spray in the range Lp = 100–200 mm, increase proportional to the increase of the current plasma flow rate in the range Ip = 400–600 A, provided that the powder feed flow Gp = 1.7 kg/h and the spraying rate Vp = 50 mm/min. Conclusion: The degree of influence of the three main technological parameters (Lp, Ip, and Gp) in the survey limit domain may be due to the selected Lp spray distance within the relatively wide recommended range of the plasma spraying equipment supplier. It is recommended to conduct the experimental planning of the L27 type to localize the optimum area

    Functional Ceramic Coatings

    Get PDF
    Ceramic materials in the form of coatings can significantly improve the functionality and applications of other engineering materials. Due to a wide range of controllable features and various deposition methods, it is possible to create tailored substrate–coating systems that meet the requirements of modern technologies. Therefore, it is crucial to understand the relationships between the structures, morphology and the properties of ceramic coatings and expand the base of scientific knowledge about them. This book contains a series of fourteen articles which present research on the production and properties of ceramic coatings designed to improve functionality for advanced applications

    Characterisation and Tribological Behaviour of Alumina Titania Coatings

    Get PDF
    Alumina-Titania coatings are excellent candidates for providing protection against abrasive wear and resistant to high temperature erosion. Such coatings are desirable in electrical insulation and anti-wear applications; viz. as protective coatings for sleeve shafts, thermo-couples jackets, pump shafts e.t.c. Plasma spraying is gaining acceptance as a development of quality coatings of various materials on a wide range of substrates. Coatings made with plasma route exhibit excellent wear, corossion resistance and high thermal shock resistance etc. Alumina pre-mixed with Titania powder (Al2O3-13%TiO2) is deposited on mild steel and copper substrates by atmospheric plasma spraying at various operating power level ranging from 11 to 21kW. The properties of the coatings depend on the materials used, operating condition and the process parameters. The plasma spraying process is controlled by the parameter interdependencies, co-relations and individual effect on coating characteristics. The particle sizes of the raw materials used for coating are characterized using Laser particle size analyzer of Malvern Instruments make. To characterize the coating, Coating interface bond strength is measured using coating pull out method with Instron 1195 confirming to ASTM C-633 standard. Micro-hardness measurement is done on the polished cross section of the samples on the optically distinguishable phases Using Leitz Micro-Hardness Tester. To ascertain the phases present and phase changes / transformation taking place during plasma spraying, X-ray diffractograms is taken on the raw material and on coatings. The coating quality and behaviour depends on coating morphology and inter-particle bonding of the sprayed powders. The surface and interface morphology of the coatings is observed by Scanning Electron Microscope. Measurement of porosity is made using the image analysis technique. To ensure the coatability of alumina- titania on different substrates, coating thickness is measured on the polished cross-sections of the samples, using an optical microscope. Coating deposition efficiency is also calculated

    High Alpha - Termisesti ruiskutetut kromioksidi- ja piikarbidiseosteiset alumiinioksidipinnoitteet. Loppuraportti

    Get PDF
    TĂ€ssĂ€ raportissa on esitetty yhteenveto termisesti ruiskutettujen alumiinioksidipohjaisten pinnoitejauheiden ja niistĂ€ eri termisillĂ€ ruiskutusmenetelmillĂ€ valmistettujen pinnoitteiden ominaisuuksista. Työ liittyy osana TTY:n Materiaaliopin laitoksella toteutettuun Tekes ‐rahoitteiseen High‐ALPHA ‐projektiin, jossa alumiinioksidipinnoitteiden korroosio‐ ja kulumisominaisuuksia pyrittiin parantamaan faasistabiloinnin avulla

    Hot corrosion behaviour of new candidates for thermal barrier coatings application in turbine simulated environments

    Get PDF
    Thermal barrier coatings (TBCs) are used gas turbine engines. The current material of choice (YSZ) degrades when it contacts with impurities arise from low quality fuels such vanadium and sulfur. YSZ cannot be used in temperature higher than 900˚C. Higher efficiency and performance of gas turbine engines will require a new generation of thermal barrier coatings (TBCs). In current work, hot corrosion behavior of new candidates including Gd2Zr2O7, ZrO2 stabilized with Ta2O5, zirconia stabilized with both Ta2O5 and Y2O3 and zirconia stabilized with CeO2 and TiO2 is investigated. For YSZ case, the reaction between NaVO3 and Y2O3 produces YVO4 and leads to the transformation of tetragonal ZrO2 to monoclinic ZrO2. Comparing to YSZ, under a temperature of 1050 °C, Gd2Zr2O7 is found to be more stable, both thermally and chemically, than YSZ, and exhibits a better hot corrosion resistance. To examine the effect of stabilizing zirconia with tantalum oxide, different compositions of ZrO2-Ta2O5 samples in the presence of molten mixture of Na2SO4 + V2O5 at 1100˚C were tested. Hot corrosion results show that orthorhombic zirconium-tantalum oxide is more stable, both thermally and chemically in Na2SO4+V2O5 media at 1100˚C, and shows a better hot corrosion resistance than the tetragonal phase. When zirconia stabilized with yttria and tantalum oxide (TaYSZ sample), minor amounts of NaTaO3, TaVO5 and Ta9VO25 are formed as the hot corrosion products with only traceable amounts of YVO4. Due to the synergic effect of doping of zirconia with both Y2O3 and Ta2O5, the TaYSZ sample has a much better hot corrosion resistance than YSZ. In zirconia stabilized with CeO2 coating, the formation of CeVO4 crystals possibly postponed the formation of YVO4 and transformation of tetragonal zirconia to monoclinic. On surface of zirconia stabilized with TiO2 coating, TiVO4 crystals are significantly smaller (about 5”m in length) than the large plate shaped YVO4 and CeVO4 found on the YSZ and CSZ samples. TiSZ coating was found to have a better hot corrosion resistance at a temperature of 1050˚C than both YSZ and CSZ coatings

    Advanced hydrophobic and hydrophilic surface treatments for non-nuclear energetics

    Get PDF
    V současnosti lze zaznamenat zvĂœĆĄenĂœ zĂĄjem o studium pevnĂœch povrchĆŻ se specifickou smáčivostĂ­ (hydrofilnĂ­/superhydrofilnĂ­ a hydrofobnĂ­/superhydrofobnĂ­) s ohledem na ĆĄirokou ĆĄkĂĄlu jejich potenciĂĄlnĂ­ch aplikacĂ­, mezi kterĂ© patƙí napƙíklad snĂ­ĆŸenĂ­ aerodynamickĂ©ho odporu, ochrana proti nĂĄmraze/odmrazovĂĄnĂ­, koroznĂ­ odolnost, ochrana proti biologickĂ©mu znečiĆĄtěnĂ­, schopnost samočiĆĄtěnĂ­ povrchĆŻ, apod. ZpĆŻsoby pƙípravy takovĂœch povlakĆŻ vĆĄak zahrnujĂ­ sofistikovanĂ© vĂ­cestupƈovĂ© postupy, kterĂ© jsou nĂĄkladnĂ© a neposkytujĂ­ dostatečnou odolnost hydrofilnĂ­ho/hydrofobnĂ­ho chovĂĄnĂ­ takto modifikovanĂ©ho povrchu. PƙedklĂĄdanĂĄ disertačnĂ­ prĂĄce je zaměƙena na (i) vĂœvoj technologickĂ©ho zpĆŻsobu vĂœroby hydrofilnĂ­ch/hydrofobnĂ­ch povlakĆŻ z materiĂĄlĆŻ odolnĂœch proti opotƙebenĂ­ s vyuĆŸitĂ­m technologie ĆŸĂĄrovĂ©ho nĂĄstƙiku; a (ii) studium pƙipravenĂœch povlakĆŻ, analĂœza jejich mechanickĂœch vlastnostĂ­ a kvality smáčivosti jejich povrchu. PrvnĂ­ část prĂĄce obsahuje Ășvod do teorie smáčivosti, volnĂ© povrchovĂ© energie, hydrofilnĂ­ch/superhydrofilnĂ­ch a hydrofobnĂ­ch/superhydrofobnĂ­ch povrchovĂœch Ășprav a pƙehled technologiĂ­ ĆŸĂĄrovĂœch nĂĄstƙikĆŻ. V rĂĄmci druhĂ©, experimentĂĄlnĂ­, části byly pƙipraveny povlaky na bĂĄzi Al2O3, Cr2O3-SiO2-TiO2, YSZ a WC-Co-Cr a analyzovĂĄno jejich smáčivĂ© chovĂĄnĂ­ s ohledem na topografii jejich povrchu. DĂĄle byly studovĂĄny povlaky YSZ s lamelĂĄrnĂ­ a kolumnĂĄrnĂ­ mikrostrukturou, s ohledem na posouzenĂ­ vlivu struktury povlaku na smáčivĂ© chovĂĄnĂ­. PrezentovĂĄn je zde rovnÄ›ĆŸ modifikovanĂœ povlak s vyuĆŸitĂ­m vysokofrekvenčnĂ­ho plasmatu. V zĂĄvěrečnĂ© fĂĄzi experimentĆŻ byly pouĆŸity tƙi rozdĂ­lnĂ© prĂĄĆĄky na bĂĄzi WC-Co-Cr pro vĂœrobu povlakĆŻ odolnĂœch proti opotƙebenĂ­ s tzv. vĂ­ce stupƈovou povrchovou topografiĂ­ povrchu tĂ©to aktivity. V rĂĄmci bylo zjiĆĄtěno, ĆŸe kombinace hrubĂ©ho prĂĄĆĄku s ultra jemnĂœmi (~500 nm) WC částicemi umoĆŸĆˆuje vznik optimĂĄlnĂ­ povrchovĂ© topografie s velmi vysokou hydrofobnostĂ­, kterou lze dĂĄle optimalizovat do superhydrofobnĂ­ho stavu pomocĂ­ dodatečnĂ© modifikace olejem na bĂĄzi Si. V poslednĂ­ části prĂĄce byla u tohoto typu povlaku stanovena odolnost smáčivosti vzorkĆŻ WC-Co-Cr pomocĂ­ testu odezvy na otěr v abrazivnĂ­ suspenzi a testu odolnosti vƯči kavitačnĂ­ erozi.Particular interest is given to solid surfaces with specific wetting behavior (hydrophilic/superhydrophilic and hydrophobic/superhydrophobic) due to their wide range of potential applications such as drag-reducing, anti-icing/de-icing, corrosion-resistant, anti-biofouling, self-cleaning, etc. surfaces. However, the production ways of such coatings are sophisticated multi-step procedures, which are expensive and do not provide sufficient robustness of the hydrophilic/hydrophobic wetting behavior. The doctoral thesis is focused on (i) the development of a technological way to fabricate hydrophilic/hydrophobic coatings from wear-resistant materials utilizing thermal spraying technology; (ii) a detailed investigation of deposited coatings, analysis of their mechanical properties and the robustness of their wetting behavior. The first part of the thesis represents a theoretical background on the wetting behavior, surface free energy, hydrophilic/superhydrophilic and hydrophobic/superhydrophobic coatings and thermal spraying technology. In the second part, Al2O3, Cr2O3-SiO2-TiO2, YSZ and WC-Co-Cr plasma-sprayed coatings were fabricated, and their wetting behavior was analyzed concerning their surface topography. Furtherly, several YSZ coatings with lamellar and columnar microstructures were studied to investigate the role of the microstructure on their wetting behavior. The effect of RF-plasma jet surface treatment is also presented. Finally, three different powder feedstocks of WC-Co-Cr were utilized to fabricate wear-resistant coatings with the so-called multi-scale surface topography. It was found that the combination of a coarse powder with ultra-fine (~500 nm) WC particles provides an optimal surface topography with a very high hydrophobicity that furtherly can be tuned into the superhydrophobic state after the additional Si-oil treatment. In the last part, the robustness of the wetting behavior of WC-Co-Cr samples was estimated by the slurry abrasion response test and the cavitation erosion resistance test.

    Thermal Spray Coatings for Electromagnetic Wave Absorption and Interference Shielding: A Review and Future Challenges

    Get PDF
    This review paper aims to consolidate scattered literature on thermally sprayed coatings with non-ionising electromagnetic (EM) wave absorption and shielding over specific wavelengths potentially useful in diverse applications (e.g., microwave to millimeter wave, solar selective, photocatalytic, interference shielding, thermal barrier-heat/emissivity). Materials EM properties such as electric permittivity, magnetic permeability, electrical conductivity, and dielectric loss are critical due to which a material can respond to absorbed, reflected, transmitted, or may excite surface electromagnetic waves at frequencies typical of electromagnetic radiations. Thermal spraying is a standard industrial practice used for depositing coatings where the sprayed layer is formed by successive impact of fully or partially molten droplets/particles of a material (used in the form of powder or wire) exposed to high or moderate temperatures and velocities. However, as an emerging novel application of an existing thermal spray techniques, some special considerations are warranted for targeted development involving relevant characterisation. Key potential research areas of development relating to material selection and coating fabrication strategies and their impact on existing practices in the field are identified. The study shows a research gap in the feedstock materials design and doping (including hollow and yolk-shelled structure types) and their complex selection covered by thermally sprayed coatings that can be critical to advancing applications exploiting their electromagnetic properties
    • 

    corecore