气体静压轴承用多孔SiC陶瓷的制备及静态性能

Preparation and Static Properties of Porous SiC Ceramic as Aerostatic Bearing

以α-SiC和β-SiC粉末为原料,羧甲基纤维素为造孔剂,制备了多孔SiC陶瓷.探讨了烧结温度、成型压力和造孔剂含量对SiC陶瓷的气孔率、显气孔率以及弯曲强度的影响,研究了用不同渗透率的多孔SiC陶瓷制备气体静压轴承的承载能力和静态刚度.结果表明:在高温下,β-SiC转变为α-SiC,同时,通过α-SiC的蒸发-凝聚过程实现了SiC陶瓷的烧结,并形成无收缩自结合结构;试样的气孔率和显气孔率随烧结温度和成型压力的增加而略有降低,但弯曲强度却增大;造孔剂含量越高,试样的气孔率和显气孔率越大,弯曲强度越低.添加质量分数为10%的造孔剂,经250MPa冷等静压成型,在2 400℃下制备的试样气孔率和显气孔率分别为28.91%和24.03%,渗透率为7.74×10-13 m2,弯曲强度为63.8MPa.因此,多孔SiC陶瓷的渗透率越低,利用它制备的气体静压轴承的承载能力越低,静态刚度就越高.

Porous SiC ceramics were prepared with α-SiC and β-SiC powders,and carboxymethyl cellulose（CMC） as the pore entraining agent.The porosity,open porosity,and the flexural strength as functions of sintering temperatures,shaping pressures,and pore entraining agent content were investigated.The load capacity and the static stiffness of aerostatic bearing assembled by porous SiC ceramics with different permeability were studied.The results show that porous SiC ceramic is able to be prepared when the β-SiC converts to α-SiC by the aggregates connection in high temperature range.The porosity and the open porosity decrease and the flexural strength increases with increasing sintering temperatures and shaping pressures.The porosity and the open porosity increases and the flexural strength decreases with increase of pore entraining agent content.For the sample with 10%（mass fraction） CMC prepared at 250 MPa and 2 400 ℃,the porosity and open porosity get respectively 28.91% and 24.03%,the permeability reaches to 7.74×10-13 m2,flexural strength is 63.8 MPa.The lower the permeability of the porous SiC ceramic,the lower load capacity and the higher static stiffness of aerostatic bearing.