Lasers find defects during machining of SiN ceramics

Citation

(1998), "Lasers find defects during machining of SiN ceramics", Sensor Review, Vol. 18 No. 4. https://doi.org/10.1108/sr.1998.08718daf.002

Lasers find defects during machining of SiN ceramics

Lasers find defects during machining of SiN ceramics

Keywords Lasers, Surface finishing

A non-contact, non-destructive, laser-based method of detecting both surface and subsurface flaws in advanced ceramics as they are machined has been developed by researchers at Argonne National Laboratory, Argonne, Illinois. The Argonne system includes a low-power (10-40mW) heliumneon laser, special optical components, optical detectors and a computer.

Researchers found that visible light from the laser can penetrate the ceramic material to various depths, depending on certain characteristics. By using special polarization optics, and carefully choosing the detected scattered light, both surface and subsurface defects can be located.

The work is important because the machining of ceramics is very time-consuming and very expensive. In fact, studies have shown that machining costs can add as much as 60-80 per cent to the cost of a ceramic part. The main reason for the high cost is the diamond-grit machining tools that are required for ceramics. In addition, any damage done to the part by the machining operation is usually not detected until the entire part has been machined.

Because silicon nitride is selected for many advanced ceramic applications, it has been the most frequently studied material. However, silicon carbide has also been investigated. The Argonne system is now being studied in a machining environment with cutting fluids and various part shapes, and the data acquisition speed is being upgraded.

The work has been funded by the Defence Sciences Office of the Defence Advanced Research Projects Agency, as well as the Office of Transportation Systems, with the Department of Energy's Office of Conservation and Renewable Energy.

For further information contact Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439, USA. Tel: 630 252 2000.