Influence of transformation toughening mechanisms of Zirconia based materials on the tribological performance under high mechanical contact loads and water lubrication

氧化锆基材料因其优异的耐磨性、高强度和韧性而经常被使用。氧化锆的强度和韧性是突出的机械性能，使其成为目前泵和密封件的标准陶瓷材料。出于这些原因，在机械负荷较高的应用中，氧化锆材料往往是首选材料。然而，在湿润滑系统中，必须研究磨损过程中的低温退化问题并使其变得可控，以确保长期成功应用。因此，该项目的目标是：a)机理、动力学和工艺参数的基本澄清；b)针对磨合阶段的退化建立现场测试程序，以研究退化和磨损之间的相互作用。基于Y掺杂四方氧化锆多晶(Y-TZP)的模型材料和含有氧化铝的复合材料(氧化铝增韧氧化锆，ATZ)将被用来研究湿润滑体系中表面相从四方相向单斜相的转变，它是环境参数(20°C到90°C之间的水润滑)、载荷条件(速度、载荷、几何形状)和处理时间的函数。相变的数量和分布的程度与微观结构的变化(裂纹扩展、残余应力和缺陷)相关，从而导致机械性能(硬度、有效弹性、韧性)和磨损性能(摩擦、质量损失)的变化。将开发一种基于X射线衍射的现场测试和校准程序，用于评估关键条件。

Zirconia based materials are often used because of their combination of excellent wear resistance, high strength and toughness. Strength and toughness of zirconia are outstanding mechanical properties which make it the current standard ceramic material for pumps and seals. For these reasons, zirconia materials are often the first choice in applications with high mechanical loadings. In wet lubricated systems, however, the issue of low-temperature degradation during wear processes has to be investigated and become controllable in order to ensure a successful application over long periods of time. Thus, the proposed project aims for a basic clarification of a) mechanisms, kinetics and process parameters and b) the establishment of procedures to test degradation in situ aiming at the running-in phase of degradation for tribological development with respect to the interaction of degradation and wear.Model materials based on Y-doped tetragonal zirconia polycrystals (Y-TZP) and a composite material containing alumina (alumina toughened zirconia, ATZ) will be used to investigate the surficial phase transformation from tetragonal to monoclinic in wet lubricated systems as a function of environmental parameters (aqueous lubrication at temperatures between 20° and 90°C), loading conditions (speed, load, geometry) and time of treatment. The extent of trans-formation in amount and distribution is then correlated with microstructural changes (crack growth, residual stresses, and defects), resulting changes in mechanical properties (hardness, effective elasticity, toughness) and wear properties (friction, mass loss). An X-ray diffraction based in situ test and calibration procedure for the evaluation of critical conditions will be developed.