Ceramic joining has become an area of widespread and increasing engineering importance as the aerospace, automotive, chemicals, metals, and utilities industries seek improved performance at higher temperature and in more corrosive service environments. The brittle nature of ceramics, the difficulty of fabricating near net-shape components, the expense of ceramic machining (requiring diamondtipped cutting tools), and the lack of reliable in-process nondestructive evaluation (NDE) methods have driven the development of a variety of joining techniques. This article discusses recent advances in ceramic joining using microwave energy as a fast, efficient means to obtain joints indistinguishable from as received material.
Ceramic materials of engineering interest include oxides such as Al2O3 and Al6Si2O13 (mullite), Si3N4, and SiC. Joining applications include attachment of components such as piston liners, combustor cans and turbine rotors in high-efficiency engines; fabrication of tube assemblies for high-temperature, high-pressure heat exchangers and temperature and corrosion resistant radiant burners; and installation of hermetic seals for vacuum system components. The most common joints are mechanical attachments which take advantage of the coefficient of thermal expansion (CTE) difference between ceramics and metals. Ceramic-ceramic and ceramicmetal joining methods using metallic, glassy, and glass-ceramic interlayers and diffusion bonding have also been successfully demonstrated in recent years.
The ability to provide rapid and volumetric heating of the parts to be joined makes microwave joining attractive. The feasibility and simplicity of this approach was first demonstrated at Los Alamos National Laboratory in 1985 by Meek and Blake, who used a home microwave oven to join Al2O3 to itself and to metal with a borosilicate glass interlayer.