Analysis of Surface Microgeometry Created by Electric Discharge Machining

Area of Science:

• Materials Science
• Surface Engineering
• Tribology

Background:

• Surface topography significantly impacts material performance and function.
• Electric discharge machining (EDM) is a key process for creating complex tool surfaces.
• Understanding the geometric properties of EDM surfaces is crucial for process optimization.

Purpose of the Study:

• To investigate the geometric characteristics of hot-work tool steel surfaces produced by EDM.
• To evaluate the effectiveness of motif and multiscale analyses in characterizing these surfaces.
• To correlate surface topography parameters with EDM discharge energy levels.

Main Methods:

• Surfaces were fabricated using EDM with varying discharge energies (150–9468 µJ).
• Topography was measured using focus variation microscopy.
• Geometric characterization employed conventional ISO parameters, motif analysis (watershed segmentation), and multiscale curvature tensor analysis.

Main Results:

• Strong correlations (R² > 0.9) were found between crater dimensions (height, diameter, area) and curvature.
• Logarithmic regression showed stronger correlations for conventional areal parameters related to height dispersion.
• Discharge energy primarily influences surface finish at larger scales, linked to crater size.

Conclusions:

• Motif and multiscale curvature tensor analysis provide an intuitive method for characterizing EDM surface complexity.
• The geometric properties of individual craters are directly extractable and quantifiable.
• Discharge energy is a critical factor controlling the scale-dependent surface finish of EDM-processed tool steels.