|Rafał Nowak, Natalia Sobczak, Tiziana Lanata, Enrica Ricci, Bartłomiej Korpała|
Surface tension of liquid tin under high vacuum was measured by the technique of large drop, using a versatile set of apparatus for high temperature testing of the properties of liquid metals and alloys. Two procedures of the metal drop surface preparation were applied, i.e. 1) the sample of tin before being placed in a vacuum chamber was cleaned mechanically and in an ultrasonic washer, 2) after the first test round, the surface of the same sample was additionally cleaned by ionic surface treatment, using for this purpose the apparatus of a unique design, which enabled the sample to be transferred directly and without the need to release the vacuum from the preparation chamber provided with an ionic gun to the high-temperature chamber. In preparation chamber, under the conditions of high vacuum, the sample was treated with ionic gun to remove from its surface the oxide nanocoating. Next, without opening the apparatus (no contact of the treated sample with air), by means of a special manipulator, the sample was moved to a transfer chamber (UHV), first, and to a measurement chamber (HV), next. The sample of tin was placed in a sapphire crucible and heated to 700°C at a rate of ~12°C/min and, as a next step, the measurements of the surface tension were taken. The next series of the measurements was taken during the stepwise (every 50°C) cooling of the sample to 300°C. The surface tension was calculated using an ASTRA-2 program developed by CNR-IENI (Genoa, Italy). The calculations were done as a part of an agreement of cooperation between the Foundry Research Institute in Cracow and CNR-IENI in Italy. The results of the calculations were included in the doctor’s thesis submitted by Ms Tiziana Lanata who was awarded a research scholarship at the Institute.
Keywords: surface tension, studies of liquid metal properties, tin, large drop method, ion etching,
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Grzegorz Moskal, Aleksandra Rozmysłowska, Andrzej Gazda, Marta Homa
Paper presents results of investigations of selected thermophysical properties of ceramics powders RE2Zr2O7 (RE - Gd, La, Nd, Sm) type, used for thermal spray coatings. In comparison also standard powder of ZrO2-8%wg. Y2O3 (Y8SZ) was tested. Using laser-flash method thermal conductivity was designated and specific heat cp by differential scanning calorimetry (DSC) was determined. Measuring temperature varried from 25-1500ºC. The samples tested were sintered at 1000ºC. As a results of tests we obtain that thermal conductivity of RE2Zr2O7 powders at 1000ºC is lower than Y8SZ. At temperature 25-750ºC higher thermal conductivity was observed for La2Zr2O7 than for Y8SZ. The highest specific heat has zirconate powder Y8SZ, and the lowest- powder based on samarium zirconate.
Keywords: thermal spray coatings, plasma spraying, specific heat, thermal diffusivity,
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Wojciech Wierzchowski, Tadeusz Grochal
A device for the fabrication of ingots from cast iron of globular non-dendritic structure of the primary phase was designed and made, using the principle of overflow on the Slope Cooling Plate, known as the SCP method. Trials were made on hypoeutectic grey cast iron and high-chromium cast iron. Even during the first trials the intended effect has been achieved, which means that a fragmentation and globularization of the primary austenite was obtained. A simultaneous effect of the applied SCP technique on the shape of graphite in grey cast iron was observed.
Keywords: cast iron, semi-solid processing, thixocasting, globular structure of iron alloys,
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Jarosław Piekło, Stanisław Pysz
The article examines possible use of analytical and numerical models of casting defects of a void type in determination of local increase of stresses in the vicinity of casting defect. The stress level can be one of the factors that will decide about the casting acceptance for service. The proposed models were examined on the example of a pressure valve made from cast iron of EN GJS 400 - 15 grade.
Keywords: casting defect, numerical model, stress, simulation of solidification process,
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