Comparative study of focus variation microscopy and SEM stereoscopic reconstruction for characterizing ablation phenomena in laser surface texturing of WC-Co material

Abstract

Scanning electron microscopy (SEM) is widely used for evaluating laser-treated surfaces, offering a broad range of magnifications and the capability to perform three-dimensional (3D) reconstructions without the need for conventional profilometers. This feature is especially advantageous in laser surface texturing (LST), where SEM is used to inspect the surfaces at different resolutions (microcracks and nanostructures), and stereoscopic reconstruction techniques enable the characterization of ablation features without additional equipment. In this study, 3D SEM reconstructions were compared with an optical measuring instrument of focus variation microscopy (FVM) to validate the accuracy of the SEM in measuring ablation diameters and depths, parameters that are critical for understanding the material behavior during laser processing. Laser treatments were applied as single lines using a solid-state pulsed laser with a 1030 nm wavelength, 1 picosecond pulse duration, 200 kHz pulse repetition rate, and different combinations of pulses per spot and peak fluence. Additionally, roughness standards were used to further evaluate surface reconstruction reliability. This work demonstrates the efficacy of SEM-based 3D reconstruction for accurately reproducing sample dimensions, as evidenced by the strong correlation with established FVM measurements. The findings validate SEM stereoscopy as a valuable and practical metrological technique. This is particularly relevant in industrial scenarios where dedicated 3D profilometers are unavailable or where the correlation of topography with elemental or microstructural analysis (e.g., Energy Dispersive X-ray Spectroscopy) is required. Discrepancies observed in a minority of cases are addressed, with potential explanations provided.