APPLICATIONS OF SCANNING ACOUSTIC MICROSCOPY IN ANALYZING WEAR AND SINGLE-POINT ABRASION DAMAGE

Wear science has historically relied heavily on observations of surfac e features to elucidate the fundamental nature of wear processes. A ho st of surface imaging techniques are currently available, each with it s own set of strengths and limitations. This paper considers the appli cation of scanning acoustic microscopy (SAM) for analysis of wear dama ge processes. Reflection-mode SAM images are produced by the interacti on of focused, high-frequency (100 MHz-2 GHz) sound waves with solid s urfaces, and contrast is produced by localized variations in near-surf ace elastic properties. A powerful advantage of SAM is its ability to probe subsurface regions where fractures and delaminations may be conc ealed from the view of traditional light-optical and electron-optical instruments. The current paper will describe the principles of SAM and illustrate several of its uses in wear surface analysis; specifically , as regards the imaging of elastic strain fields near single-point ab rasion damage in silicon carbide, in elucidating the geometry of slip line fields produced during friction tests of an oriented single cryst al of stainless steel, and in studying the highly deformed layers of a taper-sectioned intermetallic alloy of Ni3Al. SAM images are compared with photomicrographs of the same worn areas to illustrate the streng ths and limitations inherent in the technique.