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Due to the two-phase microstructure thermal micros tresses are induced to duplex stainless steels when they are exposed to temperature changes. These stresses can contribute to fatigue damage caused by cyclic thermal stresses. Thermal fatigue damage can occur with T of the cycle below 300 degrees Celsius. This kind of thermal fatigue loading is caused, e.g., by friction of rotating components and turbulent mixing and stratification of hot and cold fluids in paper and process industry.

Aim of the current study was to examine the mechanism of thermal fatigue damage formation in duplex stainless steels and to find the controlling microstructural parameters of thermal fatigue crack formation and growth. Tested materials were S31500 -type wrought steel and cast steel similar to S31803. Thermal cycle with rapid high frequency induction heating and water spray cooling was used. Samples were inspected during testing by X-ray diffraction and successive replica technique. After testing fracture surfaces were studied by SEM and dislocation structures by TEM.

Additional information

Authors: VIRKKUNEN I, Helsinki University of Technology, (FI);HANNINEN H, VTT Manufacturing Technology (FI)
Bibliographic Reference: Oral report given at: The 6th World Conference and Expo: Duplex 2000. Organized by: Associazione Italiane Mettallurgia. Held at: Venezia (IT), 17-20 October 2000
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