Laser-based optical scattering detection of surface and subsurface defects in machined Si{sub 3}N{sub 4} components

It is known that surface and subsurface defects in ceramic components may significantly affect component strength and lifetime. An elastic optical scattering technique that uses a low-power He-Ne laser, special optical components, and digital image processing has been developed to provide two-dimensional-image type data for the detection of surface or subsurface defects in machined Si{sub 3}N{sub 4} components. The technique has been used to analyze diamond ground Si{sub 3}N{sub 4} specimens that were subjected to various machining conditions. The laser scattering results were processed to obtain statistical data on machining-induced damage and were correlated with machining conditions