Microstructures And Ablation Properties Of C/C-ZrC Composites Fabricated By RMI

Abstract:Because C/C composite materials possess a series of excellent comprehensive performance like:high specific strength, high specific modulus, good toughness and strength retention rate, superior creep and thermal shock resistance in high temperature atmosphere, are considered to be excellent thermal structural materials, have received the widespread attention in aviation and space. In order to further improve the oxidation and ablation resistance of C/C composites, as meantime, avoid the drawbacks aroused by the methods of chemical vapor infiltration (CVI) and Liquid Polymer Infiltration (LPI), such as, long preparation cycle, high residual porosity, uneven ceramic phase dispersion and low content of ZrC ceramic phase, this paper has adopted a more prospectful method for application-reaction melt infiltration(RMI) to fabricate C/C-ZrC composites.Pure Zirconium and Zr2Cu alloy were selected as infiltration melts to fabricate C/C-ZrC composites, respectively. The infiltration effects of C/C porous skeleton and microstructure of as-received composites were observed, the mechanical properties and ablation behaviors of C/C-ZrC composites before and after heat treatment were studied. The results show that:(1) With the increase of matrix density, the density of as-received C/C-ZrC composite reduces. The generated ceramic ZrC particles mainly intervally distribute in the initial reinforced un-directional carbon fiber layers.The preform with medium density(1.40g/cm3) obtains the best infiltration results.(2) When select Zr2Cu alloy to fabricate C/C-ZrC composite, the phase consitution and microstructure of composite change after high temperature treatment, the bending fracture mode transforms from brittle fracture mode into pseudoplastic modle, after infiltrating and HTT for many times, finally, the bending strength increased from144.2Mpa to181.6Mpa, the linear ablation rate reduces from0.012mm/s to0.0003mm/s on oxyacetylene flame for60s.(3) When select pure Zr as melt, due to the formation of ZrO2coating at3000℃, reducing the erosion of flame, the anti-ablation properties at3000℃of the C/C-ZrC composites prove to be superior to those at2500℃.