The effects of pre-oxidation on the sintering and mechanical property of powder injection moulded SiC material

Usually, injection moulded SiC green parts are debound in inert atmosphere or vacuum, which induces the residual carbon and increases forming cycle and production cost. In this paper, injection moulded SiC with Al₂O₃ and Y₂O₃ as sintering assistant was thermal debound in air and Ar, respectively. The paper investigates the effects of pre-oxidation during debinding stage on the sintering and mechanical property of SiC material. During sintering, the oxide SiO₂ is in favour of the shrinkage of debound samples at lower temperature. After sintering, the linear shrinkage of sintered samples with pre-oxidation is bigger than the sample without pre-oxidation. Test results by TEM and XRD indicate that SiO₂ disappear from the inside of the sintered samples. The loss of SiO₂ decreases the content of Al₂O₃, which affects the formation of YAG (Y₃Al₅O₁₂). Sintered Sic samples contain α-SiC phase and intergranular phase. There is no hetero-phase between the boundaries of α-SiC phase and intergranular phase. The bending and compression strength values of sintered samples with pre-oxidation reach to 537MPa and 2.89GPa, respectively. These values approach the strength of sintered samples without pre-oxidation (594MPa and 3.0GPa).