Speaker
Description
White Etching Cracks (WEC) are complex crack networks that cause premature damage under rolling contact fatigue. Hydrogen is suspected of promoting crack formation, but its exact role remains unclear. Crack initiation and propagation are still insufficiently understood because of the interaction between microstructure, inclusions, and crack evolution.
A major challenge is that conventional microscopy provides only two-dimensional cross-sections, while WEC form intricate three-dimensional structures in the material. Three-dimensional characterization is needed to link macroscopic damage features, such as fisheye structures, with local crack initiation mechanisms.
In this work, an ultra-short pulse (USP) laser-based serial sectioning strategy is investigated for multiscale reconstruction of WEC-related damage structures. Due to the ultrashort interaction time, USP laser ablation enables rapid material removal with minimal thermal influence and reduced risk of preparation-induced artifacts. Large-area ablation followed by layer-wise optical imaging provides a fast method for three-dimensional mapping of fisheye structures and crack propagation paths.
To extend this approach to localized high-resolution analysis, a Top-Hat beam-shaping strategy is developed using a spatial light modulator.
Unlike a conventional Gaussian beam, the Top-Hat profile provides a more uniform energy distribution, enabling flatter and more reproducible material removal. The beam profile is characterized, and ablation thresholds are determined on steel to establish controlled micro-sectioning.
The results demonstrate the potential of tailored USP laser ablation and beam shaping for reproducible material removal across multiple length scales. The approach enables future correlative 3D analysis combining serial laser sectioning with electron microscopy, helping clarify the spatial relationship between crack morphology, microstructural features, and WEC initiation mechanisms.
