TWI Industrial Member Report Summary 414/1990
I A Bucklow
There is an increasing industrial interest in the use of ceramics as engineering materials in their own right, and although some engineering components will consist wholly of ceramics, there will be a major role for ceramic-to-metal joints whose formulation pose many problems not encountered in metal-to-metal joints.
In the present work, the joining of two combinations of interest to, e.g. the automotive industry, were examined, namely: partially stabilised tetragonal zirconia (PSTZ) to a spheroidal-graphite (SG) cast iron, and reaction-bonded silicon carbide (RB-SiC) to a 0.4%C steel. These combinations also embody many of the problems that will arise in other ceramic/metal joints. The specimens were simple butt joints between ceramic discs and metal stubs, and a shear tester was built to accommodate them. Joints were made by vacuum brazing with alloys based on the Ag/Cu eutectic with additions of Ti and possibly In, or by diffusion bonding via interlayers of Ti and Ag, or Ti and Cu. The brazing alloys were either in the form of commercially available foils, or as a combination of Ti coatings sputtered on to the PSTZ and used in conjunction with the simple Ag/Cu eutectic. Assessment of the joints was by sectioning and metallography, by shear testing, and by fractography of the sheared faces.