Microstructure and oxidation resistance of carbon/silicon carbide composites infiltrated with chromium silicide

In order to improve the mechanical properties and oxidation resistance of three-dimensional carbon fiber-reinforced silicon carbide composites prepared by Low-pressure chemical vapor infiltration (LCVI), electrodeposition chromium combined with silicon melt infiltration method (CSI) is developed for filling the pores of CVI C/SiC composites with chromium silicide. By this method, not only the large pores between bundles but also the small pores between fibers in a bundle can be filled. In the chemical vapor infiltration process, pyrolytic carbon interfacial layer and silicon carbide matrix layer are deposited on the surface of the carbon fiber. The open porosity of as-received CVI C/SiC is as high as 20%. Then the porous composite is infiltrated with chromium. Finally, the composite is infiltrated with silicon melt to react with chromium in the pores, thereby chromium silicide is in-situ formed and C/SiC–Cr3Si composites with open porosity of 5% is obtained. Compared with CVI C/SiC composites, C/SiC–Cr3Si composites exhibit better mechanical property and oxidation resistance. The room-temperature strength of the C/SiC–Cr3Si is 586MPa, much higher than that of the CVI C/SiC. After the CVI C/SiC–Cr3Si composite is exposed in the flame of burner rig for 20 h at 1300°C, the flexural strength of composite decreases only by 4.3%.