microscratch

Microscratch is a mechanical testing technique used to evaluate the scratch resistance and adhesion of coatings and thin films at micrometer scales. It typically involves drawing a stylus or tip, such as a Berkovich or Rockwell geometry, across a sample surface while gradually increasing the normal load. The test records how the coating and substrate respond to the advancing contact, producing data that can be correlated with material performance under mechanical stress.

The method relies on precise instrumentation that controls the tip trajectory, load, and speed, and often combines optical or electron microscopy with load-displacement measurements. Different line scratch and progressive-load scratch tests are common, and the results depend on factors such as tip geometry, loading rate, scan direction, and environment. Because the geometry and properties of the coating and underlying substrate influence outcomes, results are typically reported with detailed test parameters to ensure comparability.

Analysis focuses on identifying the onset of damage, such as cohesive fracture within the coating, adhesive failure at the coating-substrate interface, spallation, or delamination. The critical load at which damage occurs, residual scratch depth, and changes in friction or stiffness are used to assess performance. Post-test characterization and, in some cases, cross-sectional imaging help distinguish failure modes and quantify adhesion.

Applications of microscratch testing include evaluating protective coatings for automotive and aerospace components, thin-film electronics, optical coatings, and polymer coatings. It is used to compare different coating systems, optimize deposition processes, and screen materials for wear resistance. Limitations include sensitivity to test parameters, equipment condition, and interpretation ambiguity, underscoring the need for standardized procedures and consistent reporting.