Joining of sialon ceramics by a stainless steel interlayer

In direct diffusion bonding of sialon to stainless steel, thermal residual stresses arise due to the difference in coefficient of thermal expansion of the two materials. These stresses frequently lead to failure of the bond. This behaviour is further influenced by the formation of interfacial reacti on layers between ceramic and metal and the problem is essentially one of a symmetry of stresses in the interface between dissimilar materials. The pre sent study demonstrates that a thin layer of austenitic stainless steel can be used as an interlayer to join two sialon components. In such a case the distribution of residual stresses is symmetrical across the composite join and provided that the thickness of the steel layer is less than a critical value, then fracture on cooling from joining temperature does not occur. T he development of this process is described and a finite-element model has been used to predict the properties of the interfacial reaction layer betwe en steel and ceramic which are consistent with the experimental observation s. (C) 2001 Elsevier Science Ltd. All rights reserved.