~LWF0005 J MACHINING PERFORMANCE OF ZIRCONIA CUTfING TOOLS

Grain boundary phases can control the properties and performance of the engineering ceramics. It is well documented that the presence of the grain boundary phases in zirconia plays an important role in microstructural development as well as influencing the electrical and mechanical properties. The present paper deals with the techniques of fabricating and evaluating the performances of newly developed hybrid zirconia cutting tool containing ceria stabilized zirconia and yttria stabilized zirconia. INTRODUCI'ION Zirconia (ZrOJ is a remarkable material, which has attracted a great deal of attention from scientists, technologists and users. The progress in our understanding of this material and in exploiting it has been substantial[l]. The phenomenon of phase transformation of zirconia is utilized in the development of tougher grades of alumina-zirconia cutting tools[2]. The increased toughness is due to the stress-induced transformation of zirconia particles at the vicinity of a propagating crack (by absorbing the energy at the crack front), or due to the volume change from phase transformation. Ceria and Yttria are the two materials most frequently us~d in partially stabilized zirconia (PSZ). Recent machining trials on yttria-stabilized zirconia cutting tools and ceria-stabilized zirconia cutting tool have evaluated the performance characteristics[2,3]. However such materials have certain basic drawbacks. The disadvantage of Y-PSZ is that it loses its strength (degrades) when annealed in the temperature range of 200-3000C in humid air or at lower temperatures in water[4]. Such problems are not present in Ce-PSZ, because it has a very good resistance to transformation during low temperature annealing[5]. One noted disadvantage of Ce-PSZ is its lowe