Microstructure-dependent thermocyclic fatigue and damage evolution in pre-cracked tungsten-rhenium X-ray anode conversion layers

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.