化学液相渗透法制备碳化物基编织体复合材料研究

Carbon fiber preforms were infiltrated with pyrolysis carbon (PyC) and SiC using butane and methyltrichlorsilane (MTS) to prepare a three-dimensional C/SiC composite with a controlled porosity. The composite was densified and a dense coating for oxidation protection of the composite was prepared by combining chemical liquid infiltration (CLI) and reactive melting infiltration (RMI).The reactive material were infiltrated in pores of the composite by electronic deposition, a kind of CLI, at room temperature, then melted and reacted with the PyC which was infiltrated in the pores before CLI at high temperatures to form carbides. Densification by CLI combining RMI decreased the processing period greatly compared with CVI, and made the composite denser and more homogeneous than by RMI because a volume expansion of about 20~30% took place due to reaction of PyC with the melt as it infiltrates into the pores. The coating prepared by CLI combing RMI was more uniform than that by RMI, The volume expansion took place after infiltration at room temperature and increased the density, but it blocked further infiltration of the melt and then decreased the density in RMI. CLI was used to join the composite with itself as well as metals..Ni and Cr were selected as the reactive material. On the basis of microstructural analysis thermal stress of the composite, the parameters for CLI Processing were determined. Porosity of the composite was controlled in the range of 17~25%.The composite was infiltrated by CVI with PyC at 960℃ for 30 hours, then was infiltrated by CLI with Cr or Ni at 40~50℃ for 50~80 hours. As the composite was maintained at 1450℃for 30 minuets, carbide were formed. Besides the composite was infiltrated directly with silicon melt to react with chromium in the pores before PyC deposition, thereby chromium silicide was in-situ formed and a composite with open porosity of 5% was obtained. The mechanical properties and oxidation protection properties were investigated. Compared with CVI C/SiC composites, theCVI-CLI-RMI C/SiC exhibited better mechanical property and oxidation resistance. The room-temperature strength of the was 586Mpa,much higher than that of the CVI C/SiC. After the CVI-CLI-RMI C/SiC was exposed in the combustion gas for 20 h at 1300℃,the flexural strength of composite decreased only by 4.3%..

C/Sic是目前研究最多且在高推比航空发动机获应用的编织体复合材料.本项目基于燃气下C/Sic由于孔隙和热膨胀失配而发生整体失效的研究提出液相渗透法,通过渗透过程与孔隙率,冉馓己?渗透添加剂及工艺参数关系的研究,在室温下将反应性熔体材料引入用CVI制备界面层,阻挡层和热解碳的复合材料孔隙中,然后在高温下反应生成抗氧化碳化物基体.