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Possibilities of welding observation with regard of sielding gas
Rohan, P. ; Vojtíšek, Petr
MAG welding is characterized by very rapid processes in extreme condition of electric arc. To describe welding is necessary to use sufficiently quick equipment. Especially in the transition region between dip and spray transfer the processes develop quickly. Characterization of transition area in active three component shielding gas was carried out visually by hi speed camera equipment and electrically by quick response electronic measurement system.
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Objemový nanokrystalický keramický materiál připravený plazmovým stříkáním
Chráska, Tomáš ; Neufuss, Karel ; Rohan, Pavel ; Dubský, Jiří
Ceramic material based on alumina-zirconia mixture have been successfully plasma sprayed by water stabilized plasma torch (WSP®). The material is composed of three main compounds Al2O3, ZrO2, and SiO2 where the ratio of Al2O3 – ZrO2 compounds is close to the ratio in their respective eutectic alloy. The material is a refractory and exhibits very high hardness, abrasion resistance, and chemical resistance. Cast tiles of the original material were ground and sieved to obtain the right powder cut size for plasma spraying by WSP®. Both thick coatings and free standing parts with very low open porosity were easily achieved by WSP®. The feedstock powder is mostly crystalline whereas the as?sprayed material is mostly amorphous with some unmelted crystalline particles present. Electron microscopy and X-ray diffraction were employed to determine microstructure, crystallinity, and phase content of the bulk samples as well as individual splats.
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Study of the Phase Transfer in Titanium-Skandium Alloys
Brožek, V. ; Dufek, V. ; Rohan, Pavel ; Ettmayer, P.
The contribution describes the attempt to use the dilatometric method for determination of phase transformation in titanium alloys with 5wt% and 15wt% of scandium.Arc melting Ti-Sc alloys, rolling of obtained ingots and their adjustment to test probes.The dilatometric measurements proceeded to temperature 1200Cbecause even most pure accessible argon atmosphere did not prevent from.
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Plasma Spraying as a Technique for Dielectric Ceramics Preparation
Ctibor, Pavel ; Rohan, Pavel ; Kolman, Blahoslav Jan ; Dubský, Jiří ; Chráska, Pavel
This paper reports on plasma spraying of several synthetic titanetes.Ceramic materials CaTiO3-LaMg0,5Ti0,5O3,Zr0, 8Sn0,2TiO4 as well as mixture of geikielite-perovskite MgTiO3-CaTiO3 were sprayed using gas stabilized plasma gun.These materials are well know as microwave dielectrics. Plasma spraying was performed with the gas stabilized plasma gun Plasmatechnik HB4.Standard experimental techniques were used for studying of microstructure, chemical and
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