Metal-ceramic joints characterised by means of scanning laser acoustic microscope (SLAM)

The use of ceramics as structural materials presents some difficulties due to their inherent brittleness. For this reason it is suitable to use metals as structural materials joint with ceramics that are successfully tested under mechanical, thermal and corrosion loads. The use of ceramic-metal joints required the research and development of new joint methods to improve their quality and reliability and the use of non-destructive techniques to test their good quality. The brazing and thermocompression processes are two of the more interesting methods to join ceramic-metal. A preliminary non-destructive analysis of the welded area between ceramic samples (monolithic ZrO 2 or Si 3 N 4 ) and metals (stainless steel or alluminum alloys) by Scanning Laser Acoustic Microscope (SLAM) was carried out. The non-destructive analysis was used in order to detect and quantify the defect population inside the brazed and thermocompressed area, and also to get information about the change of the microstructure thanks to the use of the acoustical images.