CERAMIC AND METAL-CERAMIC COMPONENTS WITH GRADED MICROSTRUCTURE

The development of ceramic and metal-ceramic components with graded microstructures concerning material or porosity opens new fields of application. Components with different porosities combine different properties in the gradient structure regarding thermal conductivity and capacity, density, mechanical strength, and elastic modulus. Graded microstructures as combination of Iwo or more materials result in innovative, multi-functional properties combinations, such as hard and ductile, electrically or thermally conductive and insulating, magnetic and nonmagnetic for metal-ceramic composites. At the Fraunhofer IKTS the manufacturing of components with graded microstructure by multilayer technology was investigated. To demonstrate the possibilities of this technology carbon-free refractories with graded porosity, made of Ca-alurninate/Al2O3 or MgO-stabilized ZrO2, were developed to achieve properties which are equivalent to the carbon-containing refractories. Other demonstrators combine stainless steel and zirconia to address applications like filters or cutting tools. Single green tapes were manufactured by aqueous ceramic tape casting as an environmental friendly production technology. Thereby, different amounts of pore forming agents were added to the different used green tapes to adjust the porosity. To realize a graded microstructure different green tapes with defined amounts of pore forming agents were laminated to one multilayer by using a special joining suspension. SEM-images of cross-sections of the sintered components verify the perfect connection between the single layers within the sintered structures, which combines porosities between 0% and 25% (MgO-ZrO2) or 30% and 45% (CaAI) as well as steel and zirconia in one composite.