The Use of the Atomic Force Microscope in the Study of Wear

The very fine details of wear scars have been investigated using the Atomic Force Microscope (AFM). The AFM, developed some ten years ago, was designed to image molecules. However, as it has been refined, it has been used in a growing variety of applications. The instrument is essentially a very high resolution profilometer. It uses a stylus with an extremely fine point dragged over a surface. The stylus records minute changes in force as it encounters high points in the surface. It has nanometer level resolution (10^-9 meter or 0.04 millionths of an inch). The stylus is rastered over the surface and generates a three dimensional topographic map.

A number of different materials, including ceramics, steel and graphite initially subjected to wear, were examined by optical microscopy, scanning electron microscopy and atomic force microscopy. The images were compared. The study showed that each technique reveals unique features. For example, the AFM showed a binder phase in a ceramic which was more resistant to wear than the matrix and stood a few nanometers above the surface. The study showed that increased insight into wear mechanisms can be gained by multiple use of various techniques of microscopy.