| The demand of micro parts is increasing year by year with the development ofMEMS. Part with micro holes is one kind of typical microstructure product used inmedical, communication, light industry fields and so on. Ceramic materials are goingto become one of the acclaimed materials in the manufacture of micro holescomponents. Micro injection molding has a series of advantages, such as wide range ofapplication of materials, well fitness in size and shape, low cost, high efficiency, andso on. So, this process is expected to become an efficient processing of ceramic microholes components.This paper analyzed the property of mold suitable for micro injection molding.The process of feed preparation, injection molding of green part, debinding andsintering were optimized. A new kind of binder system suitable for powder injectionmolded ceramic micro holes was developed. SiC micro holes green components werefabricated by powder micro injection molding process.In order to increase the production efficiency of SiC parts by powder injectionmoulding, thermal debinding was performed in air furnace without gas shield. Theeffects of oxidation on debinding were also analyzed. Analysis indicated that air couldaccelerate the debinding rate of green parts without defects occurring. The bendingstrength of debound samples increases with the pre-sintering temperature increasingfrom550℃to850℃. Blanks debound and pre-sintered in air atmosphere under850℃have enough strength for transport. This could reduce the requirement forheating equipment, decrease production costs, and increase efficiency of debinding forSiC parts.This paper investigated the effects of pre-oxidation during debinding stage on thesintering and mechanical property of SiC nozzle with micro holes. During sintering, theoxide SiO2is in favor of the shrinkage of debound samples at low temperature. After sintering, the samples debound beforehand in air have bigger linear shrinkage than thatwithout pre-oxidation.Test results by TEM and XRD indicated that SiO2disappear from the inside of thesamples sintered at1900℃. The loss of SiO2decreases the content of Al2O3, whichaffect the formation of YAG (Y3Al5O12). Sintered samples contain α-SiC phasesurrounded by intergranular liquid phase, base on the analysis of high angle annular dartfield image. There is no hetero-phase between the boundaries conformed byhigh-resolution electron microscopy. The bending values of sintered samples withpre-oxidation reach to450MPa and600MPa. |
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