A new understanding of micromechanism analysis of rotating anode targets failure during the operation of X-ray tubes

• W-Re alloys are brittle and prone to fracture at room temperature. • Forging and heat treatment produce a deformed, subgrained microstructure in W-Re alloy, which partially dynamic recrystallizes during service. • The ablation zone exhibited a transition from equiaxed to columnar grains, with cracks propagating inward along the grain boundaries. This work presents a systematic investigation into the microstructural evolution of the rotating anode target in an X-ray tube during its service-induced failure. A consequence of the manufacturing process is a radial gradient in the anode target, characterized by a decrease in both density and hardness along the working track of these W-Re/TZM (Mo–Ti–Zr) composites. After high-temperature forging and heat treatment, the microstructure of the W-Re alloy exhibited a deformed structure with subgrains and shear bands. Conversely, the TZM alloy underwent complete recrystallization and experienced abnormal grain growth at the interface. During service, cyclic thermal stresses drive dynamic recrystallization (DRX) at the surface of the deformed W‑Re grains. This recrystallization process, which lowers dislocation density, is identified as a key mechanism responsible for the degradation of the thermal shock resistance of the W‑Re/TZM composite. Under severe fault conditions such as shaft seizure, extreme overheating causes surface melting of the W‑Re layer, leading to thermal grooving and pitting corrosion. Observations of the ablated zones demonstrated a complex microstructure, with some grains having evolved into a columnar crystal due to overheating conditions, whereas others experience conventional recrystallization. These findings highlight that controlling microstructural stability — particularly suppressing detrimental dynamic recrystallization — is crucial for extending the service life of rotating anode targets.