Joining of engineering ceramics

Abstract

Engineering ceramics such as alumina, zirconia, silicon nitride and silicon carbide can now be manufactured reliably with reproducible properties. As such, they are of increasing interest to industry, particularly for use in demanding environments, where their thermomechanical performance is of critical importance, with applications ranging from fuel cells to cutting tools. One aspect common to virtually all applications of engineering ceramics is that eventually they must be joined with another material, most usually a metal. The joining of engineering ceramics to metals is not always easy. There are two main considerations. The first consideration is the basic difference in atomic bonding: the ionic or covalent bonding of the ceramic, compared to the metallic bond. The second consideration is the mismatch in the coefficient of thermal expansion. In general, ceramics have a lower coefficient of thermal expansion than metals and, if high tensile forces are produced in the ceramic, either as a consequence of operating conditions or from the joining procedure itself, failure can occur. The plethora of joining processes available will be reviewed in this article, placing them in context from both an academic and commercial perspective. Comment will be made on research reporting advances on known technology, as well as introducing 'newer' technologies developed over the last 10 years. Finally, reviews and commentary will be made on the potential applications of the various joining processes in the commercial environment.

Microstructural evolution and characterisation of interfacial phases in Al2O3/Ag–Cu–Ti/Al2O3 braze joints

“…Between 5 h and 20 h, the Ti 3 Cu 3 O particle size and total volume decreased with time, while the opposite occurred with the titanium oxide on alumina. Small particles between $10 and $200 nm in size containing Ti and O, and therefore likely to be a titanium oxide, were also observed on SEM-EDS chemical maps in the braze alloy amongst the remaining Ti 3 …”

“…However, in general, $1 at.% Si and $6 at.% Al was identified in layer 2 at the B95/ and A95/Cusil ABA interfaces. Ca was mainly found in c-TiO grains that were dispersed in the Ti 3 …”

“…The various methods for fabricating ceramic to ceramic and ceramic to metal joints for several engineering ceramics have been recently reviewed [3]. Of these, brazing is a relatively simple and versatile technique to join similar and dissimilar materials (notwithstanding any issues relating to joint design).…”

Microstructure and mechanical properties of Si3N4/42CrMo joints brazed with TiNp modified active filler

“…Ceramic to ceramic or ceramic to metal brazing technologies are widely applied in electronic packaging and manufacturing of engines and turbines [1]. However, the poor wettability of brazing alloy on the ceramic dramatically complicates the brazing process for sound joints.…”

Fabrication of Reliable Joints of Alumina Ceramics by Microwave-Assisted Reactive Brazing Technique

“…As compared to metals the brittleness, high melting temperatures and thermal expansion mismatch properties of ceramics have created problems in finding the most suitable joining technique. 1) Brazing 2) is a joining technique, which does not involve any melting of the base metal. In this process coalescence of the filler alloy is produced by heating to a temperature higher than 450°C.…”