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2009
Conference Paper
Titel
Evaluation of fatigue damage by x-ray diffraction technique of steam turbine rotor steels at elevated temperatures
Abstract
In many industrial applications materials are subjected to degradation of mechanical properties as a result of real service conditions. The assessment of the remaining lifetime of components and structures is commonly based on correlated procedures including numerous destructive, non-destructive and mathematical techniques that should guarantee reasonable precise assessment of the current damage extent of materials in question and the remnant lifetime assessment. The assessment of the remaining lifetime by X-ray diffraction technique is based on the fact that mechanical properties of the most materials depend strongly on crystallite size and orientation of ingredients, which are the crucial parameters for the determination of the ageing state and the prediction of residual lifetime of the components. X-ray diffraction technique proved to be useful as a tool for the assessment of material degradation extent after a long-time service. Framework 5 project "XPECTION" [1] wa s dealing with this task with respect to high temperature creep degradation of boiler tube steels. In this presentation, the X-ray diffraction technique was applied to reveal subtle details of the microstructural changes induced by fatigue. Several steam turbine rotor steels were fatigue tested at elevated temperatures up to 600°C at strain control regime. After the tests, the X-ray diffraction method was used to correlate the extent of fatigue damage with the X-Ray diffraction patterns to be able to assume the life-time exhaustion caused by fatigue loading in service.