A. Gil

High-Temperature Sulfurization of Crofer 22APU in H2/H2S Atmosphere

The authors present studies of behavior of Crofer steel in H2 polluted by H2S. The high temperature corrosion behavior of Crofer 22APU steel pre-oxidized samples and not pre-oxidized ones were studied in the temperature range of 600 – 900°C in H2/H2S atmospheres in sulphur vapor pressures in the range of 10-7-10-1 Pa. Kinetics depend on the temperature and sulphur pressure, however the process of sulfurization for pre-oxidized samples was slower.

Microstructure of an oxide scale formed on ATI 718Plus superalloy during oxidation at 850 °C characterised using analytical electron microscopy

Abstract The microstructure of a scale formed on the ATI 718Plus superalloy during oxidation at 850 °C for up to 1 000 h in air was characterised using various electron microscopy techniques taking advantage of recent development and capabilities of energy dispersive X-ray spectrometry. The study shows that a protective multilayered Cr2O3 scale was formed on this alloy; the outer Cr2O3 layer was coarse-grained, while the inner one was fine-grained. Underneath, a thin layer composed of TiNbO4 as well as an internal oxidation zone that was a dozen or so micrometres thick and consisted of individual Al2O3 precipitates had formed. The growth of the Cr2O3 layer caused the appearance of a chromium depletion zone, in which the γ′ particles were not observed.

The microstructure of the Sanicro 25 steel after steam oxidation studied by advanced electron microscopy and spectroscopy methods

1International Centre of Electron Microscopy for Materials Science and Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, Kraków, Poland, 2Faculty of Materials Science and Ceramics, AGH University of Science and Technology, Kraków, Poland, 3Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, Kraków, Poland, *rutkowsk@agh.edu.pl

Oxidation of TiAl Alloys Coated by Fluorine Resin in SO2 Containing Atmosphere

There are several ways to improve the oxidation resistance of TiAl alloys. One of them is alloying with elements such as Nb, Ta, W, Si, Ag, Zr or Hf. However, bulk alloying influences the mechanical properties. Surface treatment of TiAl alloys by the small amounts of halogens leads to the formation of the protective alumina scale (“halogen effect”). The halogens can be applied by ion techniques (ion implantation, plasma immersion implantation) but also by spraying or dipping with halogen-containing inorganic and organic compounds. Deposition of the fluorine-containing resin on the surface of TiAl alloys is the easiest way to achieve the best results. SO2 impurity in air significantly influences oxidation behavior of TiAl alloys. In this work the results of the oxidation of a Ti-48Al-2Cr alloy coated with a fluorine-containing resin in the synthetic air and air containing 1% SO2 were presented. The oxidation runs were carried out in the temperature range 800-1000°C.