Process development for the ceramic injection molding of oxide chopped fiber reinforced CMCsMittwoch (05.07.2017) 15:50 - 16:10 Uhr Bestandteil von:
Ceramic injection molding is a specialized net-shaping process in the injection molding field, which combines the certain properties of ceramics like high temperature and corrosion resistance and large scale production of complex-shaped components. As further improvement oxide fibers are embedded into the ceramic-matrix to improve fracture toughness based on weak matrix concept. In this study we are trying to develop a process chain for ceramic injection molding of Al2O3 chopped-fibers (Nextel 610, 3M) reinforced CMC. The feedstocks are compounded at a certain filling degree of solid (Al2O3 μ-powder (Taimicron) with / without powder preparation and chopped Nextel 610 fibers), in which fiber content varies from 0 Vol.% to 100 Vol.%. As binder system PE + Paraffin Wax + Stearic Acid are used. The ingredients are compounded in a kneader (Brabender) at 125°C and after the viscosity measurement in the high pressure capillary rheometer at 160°C and certain shear rates, the feedstock is injection molded (Battenfeld) at 160°C, which is followed by debinding process, including chemical and thermal steps, and sintering. Flow paths in the machinery parts, rheological properties of binding system, fiber content and the fiber orientation have significant effect on the flow behavior of the feedstock, fiber orientation, -distribution & -length, which are crucial to understand the mechanical reinforcement of the fibers. The fibers in the sintered parts are ca. 200 μm in average and show different orientations in the parts depending on the form like different shear profiles in the μ-tensile-specimens. At this point the average fiber length, feedstock flow behavior and the sintering process have to be improved by process and material developments without losing flow characteristics. On the other hand, mechanical tests have to be done to characterize the reinforcement effect.