Automated Laser Scatter Detection of Near-Surface Defects and Machining Damage in Ceramic Components

The need to achieve higher gas firing temperatures in new stationary gas turbines has led to the requirement for stronger, longer-lasting materials capable of functioning in environments more severe than traditional materials permit. The higher operating temperatures seen in these environments (\u3e1300 °C) would substantially increase energy efficiency and reduce emissions. Because conventional materials are not suitable, alternate materials are being considered for turbine components. Included among these are the Si3N4 ceramics. In an effort to improve and extend the working lifetime of the components, improvement in the detection of critical defects (such as cracks, voids, inclusions, or microstructural variations) in their surface and near-subsurface regions is being investigated. Although all of the defects can occur either during manufacturing or in operation, the specific type of defect most likely to occur in a given component depends on a various factors, including the material system, processing and machining parameters, component geometry, and application environment