Study On Fabrication And Performance Of TiB₂-BN Tri-phase Electric Ceramic

TiB₂-BN multiphase ceramic is of good electricity, heat impaction resistance, machinability and corrosion resistance, and has a wide application area in metal evaporation film industry. But how to optimize the general property of TiB₂-BN multiphase ceramic is the hot popic. In this paper, TiB₂-BN-TiC/Si₃N₄ multiphase ceramic is prepared by hot press, the addition of TiC and Si3N4 and its content are studied, the relationship between the materials property and microstructure is discussed also. But in actual use, TiB₂-BN multiphase ceramic as a structural material endures high thermal shock from room temperature to working temperature and anti-aluminum erosion, so the thermal shock resistance and the erosion mechanism of aluminum to TiB₂-BN multiphase ceramic are analysized.The results show that the pressure(>25MPa) has no clear influenes on the materials property, but to TiB₂-BN-TiC multiphase ceramic, the property of the material and the relative density decease with the increase of the sintering temperature and the addition of TiC, which due to the growth of grain size, the decomposement of BN and the addition of redundant TiC particles;to TiB₂-BN- Si₃N₄ multiphase ceramic, the propety and the relative density of the material increase with the increase of the sintering temperature and decrease with the redundant addition of the Si₃N₄ phase, so improving the sintering temperature and the proper addition of Si₃N₄ can improve the general property of the materials.The optimal technics are following: the content of the additive TiC/Si₃N₄ is lwt%, sintering pressure 30MPa, the sintering temperature is 1873K of TiC and 2073K of Si₃N₄, the bending strength is 179 MPa of TiC and 142 MPa of Si₃N₄, the relative density is above 96% of TiC and above 93.5% of Si₃N₄.The thermal shock resistance results of TiB₂-BN multiphase ceramic show that the material is still intact under the imitation operating mode condition at testing temperature 1200℃ after 50 cycles, and the resistivity slightly increases with every heat cycle. But the sample will be damaged after ten cycles under the imitationoperating mode condition at testing temperature 1400°C. Besides, the working temperature has to be under strict control to be about 1200°C with no big changes happening to it, since it is another important factor influencing the life span of the composite.The process of erosion of aluminum to TiB2-BN multiphase ceramic is following such reaction through BN phase: BN+A1 — A1N+B, the main breakage mechanism include thermal shock breakage and chemistry erosion breakage, both of them can accelerate the breakage process of TiB2-BN composite.