1：Experimental Design and Method Selection:

Femtosecond laser polishing was applied to SKD 61 tool steel specimens without prior heat treatment. The study involved single-pass tracks to evaluate groove dimensions and surface polishes with varying overlap ratios to assess surface roughness and microstructure changes.

2：Sample Selection and Data Sources:

SKD 61 tool steel specimens of size 20 mm × 20 mm × 2 mm were used. Surface roughness measurements were taken at three different areas per specimen.

3：List of Experimental Equipment and Materials:

A commercial P-SpitFire-120FS femtosecond laser system (SPITFIRE PRO XP, Newport, USA) was used for polishing. Surface morphology was observed using a scanning electron microscope (SEM, JEOL FE-SEM 7001, Japan) and a roughness measurement instrument (Surfcorder, Kosaka Lab, Japan).

4：Experimental Procedures and Operational Workflow:

Laser polishing was performed with powers ranging from 0.1 to 20 mW and overlap ratios of 0, 50, and 70%. The scanning velocity was fixed at 1 mm/s.

5：1 to 20 mW and overlap ratios of 0, 50, and 70%. The scanning velocity was fixed at 1 mm/s. Data Analysis Methods:

5. Data Analysis Methods: Surface roughness parameters (Sa, Sk, Spk, Svk) were evaluated according to ISO 25178 Standard. Microstructure analysis was conducted using X-ray diffraction (XRD) and transmission electron microscopy (TEM).