Characterizing Wear with the Scanning Electron Microscope

The Scanning Electron Microscope (SEM) is used extensively to characterize and analyze wear mechanisms and coatings on material. Wear mechanisms and severity can be identified by the characteristic scars on sample surfaces and by examining wear debris. Backscattered electron imaging is very useful in identifying oxidized materials and locations where coatings have worn thin. These images are compared with spectra from energy-dispersive X-ray spectroscopy or wavelength-dispersive spectroscopy data to verify the identifications. Micrographs of typical wear mechanisms are presented and techniques for analysis of wear surfaces are discussed. Examples of the evaluation of coatings are also presented and an ultramicrohardness tester installed in the SEM to evaluate coating hardness and fracture toughness is described.