Obtenção in situ do compósito alfa-SiAlON-SiC

The objective of this work is to obtain in situ a-SiAlON-SiC composites, by silicon nitride solid solution development, during sintering, using rare earth and yttrium oxide mixture (CRE3O3) as stabilizer of the a-Si3N4 phase. A fraction of 20 vol.% of AlN-CRE2O3 mixture was mixed to 80 vol.% of Si3N4. Different contents of b-SiC powders were mixed to the Si3N4-AlN-CRE2O3 powder mixture. The powder mixtures were milled and compacted by uniaxial and cold isostatic pressing. The green bodies were sintered at 1950 °C during 1 h under 1 MPa of N2 pressure. The sintered samples were characterized by X-ray diffraction and scanning electron microscopy, in order to assess the crystalline phases and microstructural aspects, respectively. The results revealed the presence of a-SiAlON and b-SiC as the only crystalline phases present in the material. No partial crystallization of remaining intergranular phase was detected. No a-SiAlON solubility variation was observed by the use of different SiC contents, but different grain of a' grains are related to SiC addition in the mixtures.