TY - THES

T1 - Impact of Conditioning Processes on the Performance of Rotating Anodes

AU - Sommerauer, Michael

N1 - embargoed until 12-04-2026

PY - 2021

Y1 - 2021

N2 - X-ray tubes used as radiation sources for modern computed tomography (CT) systems undergo rigorous testing before their employment. The testing regime is denoted as conditioning and is comprised of three distinct sub-processes. Hereby, the rotating anode, which is one of an X-ray tube’s critical components, already experiences severe thermal and mechanical loading. Base temperatures of up to 1300 K and additional, rapid temperature rises exceeding 1000 K occur during conditioning. This leads to the appearance of first signs of surface degradation, such as thermal shock cracks, thermal fatigue cracks and local melting of the anode’s surface in specific cases. Repetitions of the sub-processes are common to ensure the tube performance is stabilized. To understand the resulting impact of such an irregular conditioning, this thesis aims to clarify the correlation between the appearance of surface degradation features and the individual sub-processes. An extensive dataset for various surface degradation features was derived by the means of sample preparation, light optical microscopy, electron microscopy, laser scanning confocal microscopy, hardness testing at various load levels, nanoindentation, electron backscatter diffraction and various other methods. Clear dependencies on the individual sub-processes, their chronological order and number of repetitions, as well as the loading parameters during conditioning and the intensity distribution of the electron beam impinging on the anode regarding various surface degradation features could be identified. Furthermore, a global impact on the dimensional change of the rotating anode on the absolute number of sub-processes could be derived. Microstructural investigations of the material under the electron beam’s impact location, the focal track, were successful in order to reveal differences between the investigated anode types.

AB - X-ray tubes used as radiation sources for modern computed tomography (CT) systems undergo rigorous testing before their employment. The testing regime is denoted as conditioning and is comprised of three distinct sub-processes. Hereby, the rotating anode, which is one of an X-ray tube’s critical components, already experiences severe thermal and mechanical loading. Base temperatures of up to 1300 K and additional, rapid temperature rises exceeding 1000 K occur during conditioning. This leads to the appearance of first signs of surface degradation, such as thermal shock cracks, thermal fatigue cracks and local melting of the anode’s surface in specific cases. Repetitions of the sub-processes are common to ensure the tube performance is stabilized. To understand the resulting impact of such an irregular conditioning, this thesis aims to clarify the correlation between the appearance of surface degradation features and the individual sub-processes. An extensive dataset for various surface degradation features was derived by the means of sample preparation, light optical microscopy, electron microscopy, laser scanning confocal microscopy, hardness testing at various load levels, nanoindentation, electron backscatter diffraction and various other methods. Clear dependencies on the individual sub-processes, their chronological order and number of repetitions, as well as the loading parameters during conditioning and the intensity distribution of the electron beam impinging on the anode regarding various surface degradation features could be identified. Furthermore, a global impact on the dimensional change of the rotating anode on the absolute number of sub-processes could be derived. Microstructural investigations of the material under the electron beam’s impact location, the focal track, were successful in order to reveal differences between the investigated anode types.

KW - Drehanode

KW - Wolfram-Rhenium

KW - Thermische Ermüdung

KW - Oberflächenschädigung

KW - Merkmal-Korrelation

KW - Rotating Anode

KW - Tungsten-Rhenium

KW - Thermal Fatigue

KW - Surface Degradation

KW - Feature Correlation

M3 - Master's Thesis

ER -