Experimental studies of the high-temperature interaction of a molten Mg-10Ca alloy (10 wt% Ca) with steel substrates were performed, for the first time, using the sessile drop method combined with ...non-contact heating and capillary purification procedure. The investigations were carried out under isothermal conditions at a temperature of 700 °C in two different flowing gas atmospheres: (i) a pure Ar and (ii) a mixture of Ar + 5 wt% H
2
. The high-resolution side-view images of Mg-10Ca/steel couples collected during the experiments were used to determine the contact angle values (
θ
) formed between the alloy drop and steel substrates. In both atmospheres, under the experimental conditions used, liquid Mg-10Ca alloy exhibited non-wetting behavior on steel substrates: after 180 s of dropping alloy from a graphite capillary, the average contact angle value in the Ar atmosphere was
θ
av
= 120°, which was slightly higher than that for the test performed in the Ar + 5 wt% H
2
atmosphere, where
θ
av
= 114°. The microstructure of the solidified couples was analyzed by scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS). The SEM/EDS analysis revealed interfacial discontinuities throughout the cross-sectioned couples and a lack of permanent bonding between the alloy drop and substrates. Moreover, neither new phases nor mass transfer through the drop/substrate interface were noted. The non-wetting and weak bonding between the alloy drops and the steel substrates is consistent with the Mg–Fe and Ca–Fe phase diagrams, i.e., the non-reactive nature of the Mg-10Ca/steel couples, since at the testing temperature, Fe does not form any compounds with both Mg and Ca, and it does not dissolve in liquid Mg.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Experimental study of the high-temperature interactions of liquid Mg with solid Ni.•Comparison of results obtained by different test procedures.•Discussion of the effect of oxide film on wetting ...behavior.•Wettability of liquid magnesium on the solid metallic nickel.•The SEM/TEM/EDS analysis of the Mg/Ni couples after sessile drop tests.
The sessile drop method was applied to the experimental investigation of the wetting and spreading behaviors of liquid Mg drops on pure Ni substrates. For comparison, the experiments were performed in two variants: (1) using the Capillary Purification (CP) procedure, which allows the non-contact heating and squeezing of a pure oxide-free Mg drop; (2) by classical Contact Heating (CH) procedure. The high-temperature tests were performed under isothermal conditions (CP: 760 °C for 30 s; CH: 715 °C for 300 s) using Ar + 5 wt% H2 atmosphere. During the sessile drop tests, images of the Mg/Ni couples were recorded by CCD cameras (57 fps), which were then applied to calculate the contact angles of metal/substrate couples. Scanning and transmission electron microscopy analyses, both coupled with energy-dispersive X-ray spectroscopy, were used for detailed structural characterization of the solidified couples.
It was found that an oxide-free Mg drop obtained by the CP procedure showed a wetting phenomenon on the Ni substrate (an average contact angle θ < 90° in < 1 s), followed by fast spreading and good wetting over the Ni substrate (θ(CP) ∼ 20° in 5 s) to form a final contact angle of θf(CP) ∼ 18°. In contrast, a different wetting behavior was observed for the CH procedure, where the unavoidable primary oxide film on the Mg surface blocked the spreading of liquid Mg showing apparently non-wetting behavior after 300 s contact at the test temperature.
However, in both cases, the deep craters formed in the Ni substrates under the Mg drops and significant change in the structure of initially pure Mg drops to Mg-Ni alloys suggest a strong dissolution of Ni in liquid Mg and apparent values of the final contact angles measured for the Mg/Ni system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Computer-aided development of liquid-assisted metallurgical processes requires reliable basic data for the molten materials, including thermophysical properties such as density, surface tension, and ...viscosity. Cast irons belong to the group of Fe-C alloys of practical importance due to their good technological and utility properties, yet experimental thermophysical data of cast irons in the literature are scarce. In this study, the density and surface tension of three compacted graphite cast iron alloys were measured by the sessile drop method in contact heating mode in the temperature range of 1473 ? 1723 K with polycrystalline alumina as a substrate. The drop profile images were recorded both during heating and subsequent cooling regimes. At 1473 K, the density values of the studied compacted graphite irons are between 6.66 and 6.69 g?cm-3, whereas surface tension values are between 1130 and 1510 mN?m-1. The density decreases with increasing temperature, while surface tension dependence on temperature is less obvious. The obtained results are compared to the available literature data and analyzed taking into account chemical interaction of liquid cast irons with the substrate material.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
High temperature behavior of three compacted graphite iron (CGI) alloys on polycrystalline alumina substrates (99.7%, porosity <3%) were examined by the sessile drop method combined with classical ...contact heating procedure in flowing Ar. High-speed high-resolution CCD camera was used for continuous recording of the CGI/Al2O3 couples during melting alloy, heating to and holding the couples at the test temperature of 1450°C for 15 min and their subsequent cooling. The comparative studies were made with conventional CGI (in wt.%: 3.70 C, 2.30 Si, 0.44 Mn, 0.054 P, 0.017 Mg, 0.015 S) and two alloys additionally containing the same amounts of 0.25 Mo, 0.1 V, 0.045 Sn and 0.032 Sb with different concentrations of Mg + Cu additions, i.e. 0.01Mg + 0.33Cu and 0.02Mg + 0.83Cu. All three CGI alloys demonstrated non-wetting behavior on the Al2O3 substrates while the contact angle values slightly decreased with increase of the Mg + Cu content in the alloy, i.e. 131° (unalloyed CGI), 130° (0.01Mg + 0.33Cu) and 125° (0.02Mg + 0.83Cu). Structural characterization of solidified couples by light microscopy and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy revealed: 1) heterogeneous nucleation of discontinuous graphite layer at the drop-side interfaces and on the surface of the drops; 2) reactively formed Mg-rich oxide layer at the substrate-side interface; 3) the formation of satellite droplets on the surface of the drops during their solidification; 4) degeneration of initially compacted graphite to lamellar graphite after remelting and subsequent solidification of the drops, particularly in their surface layer.
A critical review is given of the present state of knowledge and future perspectives in high-temperature contact angle measurement. Experimental results obtained by the different versions of the ...sessile drop method and by various procedures are given in order to illustrate the two main sources of scatter in wettability data, the first being related to the quality of the substrates and the second to control of the furnace atmosphere.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The paper presents the description of an experimental complex that has been designed for investigations of high temperature capillarity phenomena by various testing methods (classical sessile drop, ...pendant drop, dispensed drop, sandwiched drop, transferred drop, drop sucking, drop pushing, drop smearing or rubbing) at a temperature of up to 2100
°C under vacuum of up to 10
−7
hPa or in protective atmosphere (static or flowing gas with controlled rate at required level of pressure). Several examples of high temperature wettability tests are discussed in order to demonstrate the wide testing possibilities of the new experimental complex.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The wetting behaviour and interfacial interactions between liquid Al and TiB
2
ceramic have been studied by the sessile drop technique in the temperature range from 700 to 1400 °C. At about 800 °C, ...liquid Al starts to wet TiB
2
and at about 1000 °C it completely spreads over the ceramic. Al
3
Ti and Al
2
O
3
are found to be the main phases precipitating at the interface. Starting from 1000 °C, liquid Al either fill pores or penetrates along the grain boundaries of the TiB
2
ceramic. Scanning electron microscopy analysis of the interfaces evidences that the TiB
2
grains remain intact after the aluminium melt/ceramic interaction even at 1400 °C.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Aluminum matrix composites reinforced with carbon fibers (CF/Al-MMC) are promising materials for lightweight applications. So far the application has been hindered by a lack of wettability of carbon ...fibers by aluminum alloys and detrimental reactions like aluminum carbide (Al4C3) formation. Protective coatings prepared by chemical vapor deposition (CVD) could be a suitable way to overcome these problems. In this work carbon fiber based 3D-textile preforms were coated with titanium nitride (TiN). Coating thickness, homogeneity, layer structure and composition were determined. Furthermore oxidation resistance and tensile strength of coated fibers were investigated. The wettability by molten aluminum combined with an interface analysis is examined on TiN-coated graphite substrates. Finally the quality of MMC parts prepared by gas pressure infiltration (GPI) method is evaluated. The CVD process was performed with a gas mixture of TiCl4, N2 and H2. A homogeneous coating was achieved at moderate deposition temperatures in the range from 800° to 850°C and by proper adjustment of further process parameters as TiCl4 concentration and total pressure. A very thin TiN layer with a thickness between 30nm and 35nm improves the oxidation resistance and results in a moderate decrease of the tensile strength. TiN improves the wettability and acts as a protective coating. However because of the long infiltration time in the GPI process, interface reactions occur. SEM investigations of TiN coated 3D-textile preforms infiltrated with AlSi9Cu3 alloy (226D) show a completely dense composite with a strong reduction of the Al4C3 formation. TiN offers a good protective effect if the contact time with the melt is not too long.
•Every single fiber in 3D-textile preforms was coated with TiN by CVD method.•TiN layer on carbon fiber improves oxidation resistance.•A thin 35nm TiN on carbon fiber gives a moderate reduction of tensile strength.•Strong brittleness of coated fibers was caused by dominant formation of Ti–C bonds.•A suppressed Al4C3 formation at the fiber–aluminum matrix interface was resulted.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Steam oxidation study on bare and ceramic coated Haynes® 282® alloy at 800 °C for 2000 hours performed.•Nano CeO2, Al2O3, YSZ and Al2O3-Graphene oxide coatings with/out bond coat (Ni-5 wt.% Al) ...deposited on Haynes® 282® alloy using air plasma spray.•High degree of internal oxidation observed in Haynes® 282® alloy.•Plasma sprayed nano CeO2 coating with no bond coat reduced internal oxi-dation process extensively.•Al2O3 based coatings showed poor adhesion and detached from the substrate after 250 hours.
Steam oxidation test was carried out at 800 °C for 2000 h on nine plasma sprayed coatings on gamma-prime (γ’) strengthened Haynes® 282® Ni-based alloy. The lowest oxidation kinetics and extensive reduction in internal oxidation process was observed in the sample coated with nano CeO2 with no bond coat. This is due to the oxygen deficiency in CeOx that facilitates the inward movement of oxygen arising from the presence of Ce3+ oxidation state and ensures the quick formation of protective, impermeable and adherent layer of Cr2O3.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
High-temperature interactions of liquid Ti and Ti₇₄.₃Al₂₅.₇, Ti₄₉.₃Al₅₀.₇, Ti₂₆.₅Al₇₃.₅ and Ti₃.₅Al₉₆.₅ (at.%) alloys with TiB₂ ceramic are studied using the sessile drop technique. Molten Ti and ...Ti–Al alloys show a very good wetting of TiB₂. A homogeneous TiB layer with a thickness of about 20 μm forms at the Ti/TiB₂ interface. An approximately 200-μm-thick layer of densely packed TiB whiskers is observed at the interface of a Ti₇₄.₃Al₂₅.₇/TiB₂ couple. The Ti₄₉.₃Al₅₀.₇ liquid penetrates the grain boundaries in the TiB₂ ceramic and disconnects the grains in the near-interface region. The Ti₂₆.₅Al₇₃.₅ melt does not disconnect the TiB₂ grains, but penetrates the grain boundaries over a distance of about 300 μm from the interface. Ti₃.₅Al₉₆.₅ just fills the pores in the ceramic up to a distance of about 120 μm from the interface.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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