Magnetization-Shaped Method For Fabrication Of Function Gradient Material

ZrO2/Ni functionally graded material (FGM) is a typical cermets, which introduces a transitional layer between the metallic substrate and ceramic thermal barrier coating, so that the macroscopic interface is eliminated, and hence heterogeneous composites with continuously changed mechanical, physical and chemical properties are achieved. The thermal stress can be effectively relaxed in the FGM, so it can be used in high-temperature environments.For fabrication of FGM, it is not easy to obtain a continuous component distribution on the direction of thickness. To fabricate high performance ZrO2/Ni cermets with continuous component distribution is of great significance. FGM has been fabricated by vapor deposition, powder metallurgy, plasma spraying, self-propagation high temperature synthesis, electro deposition, etc.Totally different from the general methods for preparing ZrO₂-Ni cermets, in this paper, we developed a new method, which can be called magnetization-shaped method, to prepare functionally graded ZrO2/Ni materials. The preparing procedure is as follows: mixing the nickel particle, zirconia particle, and dispersant in the water to prepare mixing slurry according to a certain ratio. Then the green body is fabricated by slip casting, during which the graded magnetic field is imposed. Under the magnetic force, Ni particles move to a certain direction, and finally graded component distribution is achieved on the direction of magnetic field. After pressing the green body, removing binder and sintering in vacuum, the ZrO₂/Ni material has been fabricated successfullyThe dispersion effects of nickel slurry and zirconia slurry with different dispersant contents are studied. It is found by sedimentation experiments and scanning electron microscope (SEM) that nickel slurry has the best dispersancy when the content of PVP is 1.2wt%, and zirconia slurry has the best dispersancy when the content of PVP is 0.5wt%The viscosity of ZrC^/Ni mixing slurry with different PVP contents is investigated. It is found that the mixing slurry has the lowest viscosity when the content of PVP is 2.5wt%. The surface morphology of the slurry is examined by SEM. Results show that particles in the slurry are homogeneous with less number of conglomerations and air holes when the content of PVP is 2.5wt%.The distributions of component using different magnetic intensity are also investigated. The optical microscope and EDS analysis show that there is an obviously component graded distribution, and the component grads became greater when the applied magnetic intensity are enhanced.