重结晶碳化硅制品等静压成型研究

Fabrication of SiC electro-thermal components by isostatic pressing

传统的重结晶碳化硅制品成型方式,以干压成型、注浆成型、可塑成型为主,研究了重结晶碳化硅制品的等静压成型工艺.等静压成型重结晶制品,是将重结晶碳化硅制品的原料：50～200 μm的碳化硅粒度砂和5～20 μm的碳化硅微粉按一定比例,加上粘结性较强的水溶性纤维素和聚乙烯醇,加入成型模具,利用等静压机成型出密度高、强度大的重结晶碳化硅制品素坯.通过实验、测试分析、结果讨论,研究了成型压力、保压时间以及粘结剂含量对碳化硅制品素坯密度、强度和素坯和成品的微观结构的影响.通过扫描电镜分析：等静压成型的重结晶碳化硅制品的素坯和烧成品,致密度高,坯体中很少有气孔.研究结果还表明：随着成型压力增大,密度也不断增大,最佳成型压力为200 MPa;保压时间的长短,对素坯密度、强度也有影响,最佳保压时间为160 s,实验选用粘结剂最佳含量为2％.与传统成型方法相比,冷等静压成型所得的素坯和成品强度大、密度高、坯体均匀.

The mostly common used methods of recrystallizing silicon carbide are Dry Pressing,Slip Casting and Plastic Molding.The focus of this article is on the molding process of silicon carbide recrystallization.The manufacture of recrystallization under isostatic pressing process is to mix the raw material,50 ～ 200 μm silicon carbide sand and 5 ～20 μm fine silicon carbide powder in certain proportion combined with highly cohesive water-solvable cellulose and vinol,and then pour into the mould.The dense and strong recrystallized silicon carbide biscuit is molded under the pressure from the isostatic pressing machine.Based on the analysis of experiments and tests and the result of discussion,the impact of the molding pressure,pressure holding time,the binder and the sintering agent to the density,strength and the micro-structure of the biscuit has been researched.By analyzing the result from scanning microscope,it was indicated that the biscuits and finished products of silicon carbide molded by isostatic pressing are high in compactness and low in pore amount.It also suggests that the density is proportional to the pressure,where the best mold pressure is 200 MPa ; the length of holding time is also a factor of influence on density and strength of the biscuits.The best holding time is 160 seconds with 2％ of binder.Comparing with traditional molding method,the cold isostatic pressing molding can obtain higher strength,higher density and even more components.