Plansee SE

In the present work band sawing, electrical discharge machining, cutting by means of cut-off wheel, grinding, turning and water jet machining were examined by X-ray diffraction with regard to the development of residual stresses in the machining zone. The deformation zone could be resolved by electron microscopy and electron backscatter diffraction. In all mechanical processes, shear forces occur perpendicular to the direction of the cut. These in turn are reflected in the occurrence and magnitude of the individual stress tensor components. All mechanical processes lead to compressive principal stresses. The stress states are triaxial in nature. The shear stress components are particularly pronounced when cutting with the cutting wheel, followed by grinding and band sawing. Wire electro-discharge machining proves to be a special case.

The increasing demand for highly specialized advanced materials requires a comprehensive understanding of the relationship between processing conditions and the resulting mechanical properties. This study investigates the structure-property relationship of pure tungsten and potassium-doped tungsten fine wires, focusing on material hardness as a function of deformation state and annealing treatment. Hardness was evaluated using nanoindentation and microhardness testing, respectively. The results show a monotonic increase in hardness with increasing amount of deformation, with pure tungsten exhibiting slightly higher hardness than potassium-doped tungsten except at the highest deformation levels. The measured hardness ranged from approximately 13 GPa to 15 GPa depending on the deformation condition. Recovery annealing (400–500°C) led to further increases in hardness, indicating annealing-induced hardening effects. In contrast, high-temperature annealing up to 2400°C resulted in grain growth from approximately 100 nm to 500 nm and a corresponding decrease in hardness for potassium-doped tungsten, from approximately 8.5 to 4.5 GPa. The findings demonstrate the combined influence of deformation and thermal treatment on hardness evolution in tungsten fine wires and provide insight into microstructure-dependent strengthening mechanisms.

Rotating anode focal tracks in X-ray tubes are subjected to extreme thermal stresses during operation, leading to significant surface damage such as cracking, melting, pitting, and surface roughening. This work presents comprehensive study of the resulting surface damage on different WRe focal tracks after cyclic electron beam exposure. The experiments were conducted using a dedicated test system that enables application-relevant test conditions combined with analysis instrumentation. Measurements included the emitted X-ray dose, electron back scatter and temperatures during electron beam exposure, while post-experiment analysis primarily focused on changes in surface appearance and microstructural features of the focal track. The results provide a systematic investigation of the impact of different WRe focal tracks of rotating anodes in operational scenarios, generating deep understanding of the interaction between focal track microstructure, applied thermal loads, focal track degradation and resulting changes in X-ray emission.

The nucleation of various MoO2 starting materials was investigated on a laboratory scale during the second reduction step from MoO2 to Mo of the two-step reduction process from MoO3 to Mo. It was found that a certain proportion of gamma-Mo4O11 or a higher potassium content in the MoO2 samples as well as the addition of water to the hydrogen gas stream led to a shift from the pseudomorphic transformation towards the CVT process at a low reduction temperature of 900 degrees C. Not only spherical/polyhedral Mo nuclei but also rod-shaped nuclei were detected for the first time using the gamma-Mo4O11 containing MoO2 starting material after a short reduction time and subsequent cooling in Ar gas flow. The influence of an increased potassium content in the gamma-Mo4O11 containing MoO2 samples on the nucleation was also investigated. Additionally, a mechanism for the formation of the rod-shaped nuclei is proposed.

This study elucidates structure–property relationships governing the thermal fatigue performance of X-ray anodes for medical imaging through an integrated experimental and computational approach. Controlled surface modifications in the form of pre-induced thermal-shock crack networks were introduced into two advanced conversion layer materials with distinct microstructures and subjected to thermal loading via pulsed electron beam exposure. Characterization of surface damage evolution, the associated X-ray photon starvation, and fracture modes revealed that anodes with grains elongated normal to the surface exhibit enhanced thermal fatigue resistance. In these materials, the crack networks promote compliant deformation, accommodate cyclic thermal strains, and reduce thermally induced stress concentrations, resulting in mitigated surface damage and improved functional stability. In contrast, materials with a globular grain structure display non-uniform damage evolution, where crack deflection along grain boundaries parallel to the surface leads to delamination and accelerated surface degradation under continued thermal cycling. Computational analyses correlated the observed damage mechanisms with stress distribution–microstructure interactions. The results demonstrate that tailoring microstructural architecture and crack network morphology is critical for optimizing thermal fatigue resistance of X-ray anodes under extreme thermal loading conditions.