An automated laser-scattering system was developed for nondestructive evaluation (NDE) of ceramic engine valves. The system was used to evaluate ten NT551 (Norton-Saint Gobain) silicon nitride valves that were bench tested for 1000 hours. The bench test simulated impact and wear between the valve and the seat insert at ambient temperature. The NDE system scans the entire valve surface and generates a two-dimensional scattering image that is used to identify the location, size, and relative severity of subsurface damage. NDE data showed surface and subsurface damage from both machining and bench tests. These data were analyzed and compared with surface photomicroscopy results.
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