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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.

In support of the efforts to apply ceramics to advanced heat engines, a study is being performed of the performance of ceramics at the ring/cylinder interface of advanced (low heat rejection) engines. The objective of the study, managed by the Oak Ridge National Laboratory, is to understand the basic mechanisms controlling the wear of ceramics and thereby identify means for applying ceramics effectively. Attempts to operate three different zirconias, silicon carbide, silicon nitride, and plasma-sprayed ceramic coatings without lubrication have not been successful because of excessive friction and high wear rates. Silicon carbide and silicon nitride perform well at ambient temperatures with fully formulated mineral oil lubrication, but are limited to temperatures of 500 F because of the lack of suitable liquid lubricants for higher temperatures. Wear is confined to surface polishing during conditions of successful operation.