Papers by Keyword: Gas Corrosion

Abstract: This work shows readability of the QR code of the structural alloy Ti2 surface after the thermal influence. The main goal is the readability estimation after exposure to temperatures exceeding operating alloy temperatures and in destruction crash conditions. Contrast and readability were measured by using a Samsung smartphone and the program Adobe Photoshop CC 2017. The graphs of contrast change depending on the heating temperature were drawn. These graphs illustrate that significant changes in contrast are observed in the range from 500 to 600°C due to darkening of the base metal and the substrate, as well as fading of the dark elements of the code.

Abstract: The work is devoted to the actual problem of corrosion of the gas-collecting bell of the Soderberg electrolysis cell, which operates in close proximity to the molten electrolyte. Due to gas corrosion during the operation of the electrolysis cell, the cast-iron sections are destroyed and the release of anode gases into the atmosphere of the housing occurs. Iron-containing corrosion products falling into the melt of primary aluminum reduce its quality and grade. In order to prevent this phenomenon, the effectiveness of their protection with a dry mixture for obtaining a protective oxide-ceramic coating of cast-iron surfaces of gas-collecting bell is studied. The results obtained proved the effectiveness of the proposed coating: the service life of the gas-collecting bell sections increased by 4 times. After applying the protective coating for A85 grade aluminum, it increased from 2 to 24%, and the share of A7 grade aluminum decreased from 25 to 18 %.

Abstract: The dependence of the rate of gas corrosion of high-alloy steels on temperature is investigated in this article. High corrosion resistance of steels is achieved by introducing into their composition of elements that form thin and strong oxide films on its surface. The most effective alloying elements are chromium, aluminum and nickel. Steel, containing these elements, becomes resistant to gas corrosion at high temperatures. Steels, containing less chromium, are susceptible to gas corrosion to the same extent as carbon steels. The steel 310 S and 316 Ti were tested for heat-resistance. Samples of steel 310 S were cut from a new pipe and from the coil of pyrolysis furnace, which was used for 6800 hours. Tests were carried out at 500 ... 1000 °С. It is established that steel 310 S is more heat-resistant than steel 316 Ti. It is shown that the heat-resistance of steel 310 S decreases after operation in the pyrolysis furnace and has lower values than values of the new steel.

Abstract: Heat-resistance (scale resistance) is the steel corrosion fastness in dry gas at high temperatures. At the temperatures over 570 °С, the ferrous alloys oxidize, as ferric oxide (wustite) with simple cubic lattice appears on the metal surface. Such oxide lacks oxygen atoms (omission solid solution) and does not interfere with the diffusion between metal and oxygen. As a result of this process the brittle oxide-scale develops and the loss of metal increases. In order to increase the heat-resistance of steel, different alloying elements are included into its composition, forming oxides with the tight structure of crystal lattice. In this paper we’ve investigated the heat-resistance of some structural steels and analyzed their corrosion resistance in the high temperature aggressive environments of chemical productions.

Abstract: γ-titanium aluminide a promising structural material for automotive and aircraft applications at high temperatures suffers from poor gas corrosion resistance. It has been proved in this work by means of microthermogravimetry and SEM, EDS, EBSD and X-Ray diffraction carried out and under isothermal conditions and thermal cycling that a great improvement of the oxidation resistance of this material can be achieved due to magnetron sputtered coatings of γ-TiAl with vatious additions (Ag, Cr, Mo, Nb, Si or Ta) or their combinations. The oxidation rate of some of these coatings is four orders of magnitude smaller than that of the bare γ-TiAl substrate.