3D microanalysis of iron segregation based on picosecond laser-induced breakdown spectroscopy imaging

Abstract

The elemental microanalysis plays a crucial role in gray cast iron quality control, and segregation monitoring is an essential step in this analysis. In this study, we developed a three-dimensional laser-induced breakdown spectroscopy (3D LIBS) system for examining gray cast iron using a 9 ps-pulsed laser operating at 355 nm. 2 μm high spatial-resolved measurements were successfully achieved to determine the 3D segregation of Copper (Cu), and Manganese (Mn). In terms of experimental methodology, this study has overcome the limitations of traditional three-dimensional imaging techniques by abandoning conventional approaches that rely on physical sectioning to acquire depth information. Instead, it adopts a more efficient and non-destructive strategy: performing mapping ablation cleaning under laser defocusing conditions to eliminate interference from surface impurities or previously analyzed regions, followed by 3D LIBS imaging implementation with precisely focused laser beams. Through the ablation theory formulas, the axial ablation depth under laser irradiation was precisely calculated as 2 μm, thereby obtaining a total of 12 layers of depth-resolved data while maintaining stable and reliable signal-to-noise ratios (SNR) for each layer. The microscale 3D LIBS analytical technique provides a powerful tool for understanding the distribution patterns of various segregated elements in gray cast iron materials. Therefore, 3D LIBS has been demonstrated as an effective technology for addressing elemental segregation and can serve as an alternative methodology for gray cast iron quality inspection.