Filtern
Dokumenttyp
Schlagworte
- Friction (3)
- Stainless steel (3)
- Cryotechnology (2)
- Phase transformation (2)
- Stacking fault energy (2)
- X-ray diffraction (2)
- Austenitic steel (1)
- Austenitische Stähle (1)
- CrNi steel (1)
- Cross-sectional transmission electron microscopy (1)
- Cryoengineering (1)
- Deformation (1)
- Gefüge (1)
- Hydrogen (1)
- Hydrogen absorption (1)
- Liquid hydrogen (1)
- Low temperature (1)
- Martensit (1)
- Martensitbildung (1)
- Martensite (1)
- Microstructure (1)
- Rostfreier Stahl (1)
- Röntgendiffraktion (1)
- Tiefe Temperaturen (1)
- Transformation (1)
- Tribologie (1)
- Wear (1)
- White etching layers (1)
Eingeladener Vortrag
- nein (1)
Hydrogen represents an important alternative to fossil fuels. Hydrogen storage is possible as a gas, at room temperature (RT) at about 20 MPa pressure, and in a liquefied form, at cryogenic temperatures of about 20 K. The latter form is particularly attractive due to the possibility of stocking a large quantity of hydrogen within a small volume. In moving parts (e.g. of transport vehicles) cryogenic temperature and the presence of hydrogen strongly enhance wear processes and subsequently component failure.
The present work deals with the deformation behaviour and the microstructural deterioration of austenitic CrNi- and CrMn high nitrogen-steels during friction in liquid hydrogen at 20 K. The modified microstructure within the wear scar is studied by scanning electron microscopy and X-ray diffraction methods. Diffraction studies of wear scars reveal the importance of twinning during deformation at 20 K. This increase of twinning can be attributed to a hydrogen-induced reduction of stacking fault energy (SFE) in the austenitic steels. Interactions between twin boundaries and planar dislocation structures along with locally increased stresses led to the formation of extensive crack networks. The amount of hydrogen-induced surface cracks depends on the alloy composition and is not necessarily correlated to the wear resistance of the austenitic steels.
Verformung und Gefügetransformation bei Schwingungsverschleiß von austenitischen FeCrNi-Legierungen
(2004)
Phase stability of AISI 304 stainless steel during sliding wear at extremely low temperatures
(2003)
For applications at extremely low temperatures of a few Kelvin, austenitic FeCrNi alloys usually are employed due to their beneficial mechanical and magnetic properties. These properties depend on the stability of the austenitic microstructure, since transformation into martensite leads to a loss of ductility as well as to the formation of ferromagnetic regions. The necessary conditions for the transformation into martensite are present in case of components subjected to friction, e.g. in machine parts used for transportation of cryogens, especially of liquid hydrogen. The transformation behaviour at low temperatures is studied on friction stressed FeCrNi steel AISI 304 by magnetic measurements and by diffraction methods.
Patches of white etching layers on rail surfaces were investigated using sophisticated techniques like cross-sectional transmission electron microscopy (XTEM) and synchroton X-ray diffraction. Optical microscopy failed to resolve the microstructure, but in the TEM submicron grains with high dislocation densities and occasional twins, which are characteristic features of high carbon martensite, were observed. The martensitic structure was confirmed by evaluation of synchroton X-ray diffraction line profiles. The latter technique also allowed to determine dislocation densities of the order of 1012 cm-2 and residual compressive stresses of about 200 MPa.