Grinding of transformation-toughened mixed oxide ceramic

During the manufacturing of ceramic components, grinding is an important manufacturing step. It influences the workpiece quality and the operational reliability. Thermomechanical loads during grinding can influence the lifetime and operational reliability of ceramics by modifying their bending strength and subsurface properties. Therefore, it is necessary to consider the influence of the grinding forces and mechanical loads on the strength of the ceramics in order to design a suitable grinding process. In this investigation, a quick-stop device is used to interrupt the grinding process of the newly developed mixed oxide ceramic SHYTZ (strontium hexaaluminate/yttria-toughened zirconia) and the market-established ceramic ATZ (alumina-toughened zirconia). Subsequently, an analysis of the occurring material removal phenomena, the number of active abrasive grains, and the real thermomechanical loads is carried out. It was found that the number of active grains and the material removal phenomena are influenced by the tool specifications. Besides that, the experimentally determined number of active grains was found to be up to 14 times higher than predicted by an analytical model given in literature. Consequently, the calculated single grain chip thickness was found to be up to 12.1% lower than analytically predicted. The investigation of the process forces and thermal loads showed up to 52% higher loads for ATZ than for SHYTZ. The subsequent analysis of the resulting bending strength of the ceramics revealed a lower influence of the grinding process on the strength of SHYTZ than for ATZ. Furthermore, a correlation between the used tool bonding and the resulting thermomechanical loads, bending strength, and residual stresses could be observed.