V. E. Annamalai

Efficient grinding of Ce-TZP with SiC wheels

Abstract Transformation toughened zirconia has been widely studied. Most of the reports on zirconia deal only with the transformation behaviour in various environments. However, for the effective use of any ceramic, information on processing is essential. In spite of stabilized zirconia being an important material for various technical applications, details on how it can be processed by grinding is lacking. The present paper reports on the grindability of ceria-stabilized zirconia with various grinding wheels. Based on the grinding forces, specific grinding energies, phase structure and grinding induced surface cracks, it is shown that SiC grinding wheels can grind Ce-TZP efficiently.

CBN wheel grinding of alumina and partially stabilized zirconia ceramic-ceramic composites

Abstract Composites of alumina and partially stabilized zirconia have good functional properties such as high hardness, high strength, high thermal resistance, good chemical inertness, low thermal conductivity and high fracture toughness value. These properties make it a prospective material for tribological applications and metal cutting. This requires critical dimensional tolerance and surface finish. To meet this efficient and precision machining technologies are needed. CBN wheel grinding of this ceramic-ceramic composite has resulted in a surface with good texture and finish.

Grinding of transformation toughening ceria stabilized tetragonal zirconia polycrystals

Abstract Tetragonal zirconia polycrystals undergo phase changes under the influence of stress and temperature. Grinding, with its associated stress and temperature, can trigger these transformations. Hence, the choice of grinding parameters should be based not only on the force pattern and surface finish but also on the surface damage due to phase transformations. In the present work, the grinding parameters are assessed for sintered ceria stabilized tetragonal zirconia by conducting grinding studies, the nature of surface production being discussed.

Cutting tool application of ceria-zirconia

Abstract Transformations between the tetragonal and monoclinic phases of stabilized zirconia, popularly known as transformation toughening, have been widely studied. The transformation response of these phases to temperature and stress are quite different and hence their transformation response to an environment such as metal cutting, where both temperature and stress effects are involved simultaneously, is of interest. Since any processing may lead to transformations and phase changes, there has been no report on the application of these transformation toughening materials. The present paper deals with the techniques of fabricating a ceramic cutting tool based on ceria stabilized zirconia without phase destruction. The machining performance of this tool in machining cast iron is evaluated and its transformation behaviour in the metal cutting environment is studied.

Etching behaviour and associated transformation of stabilized zirconia

Ceramography of stabilized zirconia is a difficult task, often requiring hot etching [1]. In previous work we developed a technique of mechanically weakening the grain boundaries by ultrasonic machining and then etching at room temperature [2]. Reports on pure (unstabilized) zirconia show that microstructures could be attained even without etching [3]. The major difference between the stabilized and unstabilized forms of zirconia is the presence of the tetragonal (t) phase in the former and its absence in the latter. The fact that unstabilized zirconia does not need etching means that the monoclinic (m) phase of zirconia does not need etching. Similarly, the fact that stabilized zirconia is difficult to etch simply means that t-phase is not easily etched. However, etching is based totally on differences in the chemical composition of the surface [4]. Accordingly, an etchant that is capable of etching zirconia should be able to do so irrespective of the physical structure of the zirconia, i.e. irrespective of whether it is in m-phase or t-phase. Therefore, the difficulty of etching zirconia samples containing t-phase particles needs explanation. In order to assess the etching behaviour of the different phases of zirconia, two samples were chosen: sample A with 33.9% t-phase (the remainder being m-phase) and sample B with 100% t-phase. Both samples were prepared from 12 tool % ceria-stabilized zirconia (TOSOH, TZ-12CE), by dry pressing with a suitable binder and sintering. Sample A was sintered at 1600 °C for 2 h, furnacecooled and subsequently heat-treated at 400 °C for 2 h. Sample B was sintered at 1350 °C for 2 h and air-quenched (i.e. removed from the furnace soon after the soaking time was over and allowed to cool in still air). These sintering schedules were selected from previous experiences [5] of tailoring the phase structure in 12 mol % ceria-stabilized zirconia. Normally, surfaces are polished before etching. However, in zirconia there are numerous reports on the t-to-m phase transformation arising due to various stress inducing environments such as machine grinding [6-8], electron-beam heating during transmission electron microscopy observation [9] and even indentation [10]. In particular, 12 mol % ceria-stabilized zirconia is highly transformable and t-to-m phase transformation in this material has been reported even due to polishing [11]. Since polishing would induce t-to-m phase transformation,

Mechanical properties of low-temperature sintered ceria-stabilized tetragonal zirconia phase Part III Thermal shock resistance

Weibull fracture concerns ial. It has been established that ceria-stabilized tetragonal zirconia phase (Ce-TZP) can be fabricated from 12mo1% ceria-stabilized zirconia powder (TZ-12Ce) by compacting and sintering at 1350 °C [1]. The mechanical properties of this low-temperature sintered Ce-TZP are being evaluated. Part I of this series dealt with the bending strength and modulus [2] and part II dealt with the toughness [3]. The work reported here the thermal shock behaviour of this mater-

Lapping of composites of alumina and partially stabilized zirconia

Abstract The advanced ceramic products are usually fabricated from fine powders through powder processing techniques. In order to use these materials for engineering applications, machininh, either for imparting a shape change or for attaining a desired level of surface finish, is essential. Grinding followed by lapping improves the surface finish of the composites of alumina and partially stabilized zirconia.