ABSTRACT
Two commercially available grades of polycrystalline alumina, Dynallox 96 and Dynallox 100, manufactured by CoorsTek Ltd, Crewe, UK, were used to produce test bars of two different geometries. According to the materials data sheets supplied by CoorsTek Ltd, the average flexural strengths of D-96 and D-100 alumina ceramics, measured at 20°C, are 360?MPa and 350?MPa. Despite differences in the purity of these alumina ceramics, both materials provide similar flexural strengths. Arithmetic mean surface roughness measurements were made using a Zeiss Surfcom 130A stylus contact profilometer. Alumina-to-alumina brazed joints, whereby short test bars were brazed to themselves, were prepared by first arranging short test bars into butt-joint assemblies. Several vertically aligned joint assemblies were supported in a bespoke stainless steel fixture, which was designed to allow uniform heating of each joint interface during brazing. Mounted and polished sections of the standard D-96 and D-100 test bars were etched using two different techniques; thermal etching and chemical etching.
