Fabrication And Characterization Of Machinable Ceramic Ce-ZrO₂/CePO₄

Layer structured CePO₄ was added to ZrO₂ ceramic matrix to improve the machinability of the composites .The composites can be machined using conventional metal-working methods and have been widely used owning to their chemical stability,high melting point,excellent oxidation resistance and weak interfaces bonding.At first,CePO₄/Ce-ZrO₂ powder was prepared by mechanical mixed method; secondly,the powder was formed in mould under 190 MPa pressure; at last,the green bodies were sintered at different temperatures. Relative density and SEM indicate that ceramic composite in this series of experiments mostly are sintered compactly, component distributing and crystal grain granularity are uniform . Only the samples sintered at 1400℃have little pore. Relative density of the samples sintered above 1450℃are better than 96% .This paper discussed that the effects of sintering temperature and the components of the material on the mechanical properties and machinable exponent. According to fracture toughness and hardness, we get the machinable exponent all kinds of sample.The exponent not only reflects machniability,but also mechanical properties of the materials. The results of experiment showed that the material sintered between 1500℃to 1550℃have higher relative density,mechanical properties and machining exponent,then the material has good machinability as well as maintaining outstanding mechanical properties. The hardness decreased with the content of CePO₄ increased; When the content of CePO₄ was 25% , the bending strength,machinable exponent and fracture toughness reach the highest value.By analyzing the microstructure combining with mechanical properties of materials, the machinable mechanism of materials has been researched and analyzed. From the microstructure of fracture surface we can find the layered crack in bigger CePO₄ grain and that most ZrO₂ grains rupture along grain boundary. With the content of CePO₄ increased, more layered crack appeared. After machining, the damage to the surface of samples has been lowered.Machinable mechanism for CePO₄/ZrO₂ Ceramic composite can be brought about from two aspects: the layered crack of CePO₄ and the weak combination with CePO₄ and ZrO₂ crystal grain. They are the main reasons resulting in CePO₄/ZrO₂ ceramic composite can be easily machined.