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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% H2. 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 θav = 120°, which was slightly higher than that for the test performed in the Ar + 5 wt% H2 atmosphere, where θav = 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. [ABSTRACT FROM AUTHOR]

The high-temperature interaction between molten gray cast iron and Ti + C substrates that are composed of titanium and graphite powders was investigated by the sessile drop method combined with the non-contact heating of an alloy/substrate couple to a test temperature of 1330 °C in an inert gas atmosphere (argon). During the high-temperature testing, the images of the couple were recorded by a high-speed high-resolution CCD camera and used for estimating the values of the contact angles over time. An analysis of the wettability kinetics of the different Ti + C substrates by molten cast iron as well as a detailed structural characterization of the solidified couples with the help of light microscopy, electron microscopy (SEM, TEM), X-ray diffraction, and energy-dispersive X-ray spectroscopy have allowed us to explain the mechanism of high-temperature interaction in the selected couples. It was evidenced that the good wetting and fast infiltration of all of the examined substrates with the selected alloy had a reactive nature due to the dissolution of the Ti and graphite in the molten alloy (dissolutive wetting) and the reactively formed wettable TiC phase. These high-temperature phenomena contributed to the formation of three metal-infiltrated zones with different amounts and distributions of TiC particles in the Fe-based matrix. [ABSTRACT FROM AUTHOR]

High-entropy silicide (HES) coatings are a promising solution to the problem of poor oxidation resistance of metallic refractory alloys. However, their practical development is still in the early stages. For the first time, this study evaluates the feasibility of synthesizing complex concentrated silicide coatings using a reactive melt infiltration approach. For this purpose, a sessile drop experiment was carried out in which a binary eutectic silicon‑boron alloy (Si 8B at.%) was subjected to contact heating with the MoNbTaW refractory high entropy alloy (RHEA) substrate at temperatures up to 1450 °C. After the high-temperature test, the solidified couple was characterized by X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, electron backscatter diffraction systems, and microhardness techniques. The coating had an average thickness of 75 μm and was composed of different layers, including a primary MSi 2 layer, a transition MSi 2 + M 5 Si 3 silicide layer, and M 5 Si 3 silicides (M = metal). Additionally, borosilicides and boride particles were dispersed throughout the layers. However, future research should prioritize refining process parameters to eliminate porosity and improve the integrity of the coating layer. [Display omitted] • First proof of concept of synthesizing complex concentrated silicide coatings via liquid-assisted method. • Successfully synthesized multilayer silicide-based coating on MoNbTaW alloy using molten Si-B alloy. • Showcases silicide-based coatings can be produced in one-step under pressure-less conditions without chemical activators. • Formation of a multilayered coating, with MSi 2 and M 5 Si 3 as the main phases plus minor quantities borides and borosilicides. [ABSTRACT FROM AUTHOR]

In this paper examinations of high-temperature wetting tests of 3 systems of liquid alloy – cast iron in contact with ceramic materials: magnesia ceramics in combination with natural graphite were presented. After wettability testing, the microscopic observations of the morphology of the sample surface and the cross-section microstructure with the chemical composition in micro-areas were examined. One of the objective of this work was also to verify whether the graphite content would affect the wettability of the magnesia ceramics. The study of high-temperature wetting kinetics of the liquid alloy in contact with the ceramic material, by the "sessile drop" method with capillary purification (CP) procedure was conducted. Under the test conditions, at a temperature of 1450°C and time 15 minutes, all 3 experimental systems showed a non-wetting behaviour. The average contact angle for the system with cast iron drop on magnesia ceramics was 140°, on magnesia ceramics with 10 parts per weight of graphite was 137° and on magnesia ceramics with 30 parts per weight of graphite - 139°. Microscopic observations revealed that in the case of the sample consisting of the cast iron drop on the substrate with magnesia ceramics, the formation of fine separations was not observed, unlike the systems with the substrate with magnesia ceramics and the addition of natural graphite. Numerous, fine droplets accumulate on the graphite flakes and consist mainly of Si as well as Fe and O. On the other hand, the rough MgO grains have a gray, matt surface, without fine separations. The conducted observations indicate the mechanical nature of the bonding - liquid metal penetrates into the pores of the rough ceramics of the substrate. However, in the case of systems of cast iron drop with magnesia ceramics and addition of graphite, probably the adhesive connection and the physical attraction of elements derived from cast iron drop with the flake graphite appeared as well. [ABSTRACT FROM AUTHOR]

In this paper, temperature and concentration dependencies on density and surface tension of liquid Fe-C-O-Cr alloys (1.93 - 4.80 wt.% Cr) were investigated in high-temperature resistance observation furnace by a sessile drop method during heating from liquidus temperature to 1600 °C. The interfacial characteristics (interfacial tension, wetting angle, work of adhesion, and spreading coefficient) of liquid alloy/alumina system were also determined depending on temperature. The effect of temperature and chromium content on surface and interfacial properties was proven in case of all examined alloys. Based on the fact that the content of surface-active elements such as oxygen (up to 195 ppm) and sulfur (up to 545 ppm) was higher, the influence of activities of both mentioned elements on surface tension of alloy samples was assessed. Particular attention was paid to the dependence of the surface tension temperature coefficient on oxygen and sulfur activity. [ABSTRACT FROM AUTHOR]

• Experimental assessment of a novel liquid-assisted borosiliconizing process. • A new technological approach for a fabrication of Mo-Si-B materials. • Wetting, spreading and reactivity in Si-B/Mo system. • Reactively formed molybdenum silicides, borosilicides and borides. In this work, we used a sessile drop experiment to assess a feasibility of novel processing design engaging liquid-phase assisted fabrication of multi-phase materials from Mo-Si-B system. For this purpose, binary eutectic silicon-boron alloy (Si-3.2B wt%) was subjected to contact heating with polycrystalline molybdenum substrate at temperature up to 1385 °C. It was in-situ observed that molten Si-3.2B alloy wets and rapidly spreads over the Mo surface. After the high temperature test, the solidified couple was subjected to structural characterization by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray diffraction methods. The obtained results revealed that the direct interaction between examined materials under applied testing conditions results in the reactively formed product layer having a thickness of ∼80 µm. The following structural features were recognized starting from the surface side: (I) the main product layer composed of columnar-like MoSi 2 phase and Mo 5 Si 3 phase; (II) an intermediate layer made of MoB and Mo 5 SiB 2 phases. Although these results give the first indication for designing a novel liquid-assisted fabrication method of Mo-Si-B materials, an existence of porosity in the product layer clearly suggests that a further optimization of the process parameters is necessary. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the experimental performance of a new testing device designed for investigating the high temperature properties of molten Mg is presented. The newly developed device allows examining high temperature wetting behavior and thermophysical properties of molten Mg (and Mg alloys) by using various experimental procedures (e.g. classical sessile drop, pendant drop, dispensed drop and drop sucking). High temperature wettability tests at temperatures up to 1000 °C in an inert gas atmosphere or under high vacuum (up to 10−7 hPa) are now possible. It has been documented that the application of the classical sessile drop method combined with a capillary purification procedure successfully eliminates the problem of magnesium oxidation that traditionally affects obtained results. Selected examples of high temperature experiments carried out for molten Mg in contact with various refractories are presented in order to show a wide range of analytical possibilities of the new device. The results obtained by using the new device are important from both a high theoretical and practical perspective regarding liquid phase assisted fabrication and processing of Mg-based alloys and metal-matrix composites. [ABSTRACT FROM AUTHOR]

The study involved measurements of surface tension of liquid binary copper-bismuth alloys with respect to their chemical composition and temperature as well as investigations of the liquid alloy - refractory material - gaseous phase system wettability using usual refractory materials, i.e. aluminium oxide, magnesium oxide and graphite. The experiments were performed with the use of sessile drop method and a high-temperature microscope coupled with a camera and a computer was utilised. [ABSTRACT FROM AUTHOR]

Abstract: The density of binary Ni–Al alloys with aluminum concentration from 0 to 20wt% in liquid state was measured by a modified sessile method (MSDM). It was found that the liquid density of Ni–Al alloys decreases with increasing temperature and Al concentration in the alloys, while the molar volume of liquid Ni–Al binary alloys increases with the increase of temperature and Al concentration. The partial molar volume of Al in liquid Ni–Al binary alloy was calculated approximately. The molar volume of liquid Ni–Al alloy determined in the present work shows a negative deviation from the ideal linear molar volume. [Copyright &y& Elsevier]

Abstract: The surface tension of molten Sn–Bi (mole fraction ) alloy has been determined by the sessile drop method at oxygen partial pressure of and different temperatures. The experimental results have been analyzed and discussed, and the positive temperature coefficient of surface tension of molten Sn–Bi alloy has been elucidated. The surface tension of this molten alloy has also been obtained by calculation using STCBE based on Butler''s equation and thermodynamic data. The experimental results agree well with the calculation values. [Copyright &y& Elsevier]