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HIGH-TEMPERATURE CREEP BEHAVIOR OF REINFORECEMENT FIBERS FOR CERAMIC MATRIX COMPOSITES AND CHARACTERISTICS FOR SEVERE ENVIRONMENTS

陶瓷基复合材料增强纤维的高温蠕变行为及恶劣环境特性

基本信息

批准号：
11450255
负责人：
OKAMURA Kiyohito
金额：
$ 7.3万
依托单位：
OSAKA PREFECTURE UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

Three types of SiC fibers for reinforced fibers of ceramic-matrix composites (CMC) are commercially available ; Nicalon (SiC_<1.34>O_<0.36>), Hi-Nicalon (SiC_<1.39>0_<0.01>) and Hi-Nicalon-Type S (SiC_<1.05>). The first fiber contains an amorphous silicon oxycarbide (SiC_XO_Y) phase, next one is low-oxygen contained fiber and is microcrystalline, and finally, nearly stoichiometric sintered SiC fiber. Such differences in oxygen content and microstructure may greatly affect the properties of the fibers at high temperatures in different environments. Under high and moderate oxygen partial pressures, the SiC fibers are passively oxidized and the resulting stable silica film protects the material from further oxidation. Under low oxygen partial pressures, the SiC fibers are subjected to active-oxidation accompanied by the formation of gaseous products, resulting in serious damage to the SiC fibers. In the present work, these SiC fibers were oxidized at 1773K in Ar-O_2 gas mixtures with oxyg … More en partial pressures (po_2) from 1 to 10^5 Pa to investigate the active-to-passive oxidation transition. The active-oxidation occurred at po^2≦100 Pa for Nicalon, po^2≦10 Pa for Hi-Nicalon and po^2≦1 Pa for Hi-Nicalon-Type S. The po^2 values are dependent upon the amounts of SiC_XO_Y phase. On the other hand, it is important to investigate creep behavior of these fibers in order to obtain a better understanding of the reliability for reinforcement of high temperature CMC. Tensile creep tests were performed on single filaments in air and Ar gas at 1573-1723 K with an applied load of 0.35-0.75 Gpa. The creep apparatus was originally produced with the support by Grant-in-Aid for Scientific Research ((B)(2)). From the values of the stress exponents and the activation energies for creep in air and Ar gas, the creep deformation mechanisms of Nicalon, Hi-Nicalon and Hi-Nicalon-Type S are associated with the grain-boundary diffusion, grain-boundary sliding and the movement of dislocations, respectively. The differences between the creep parameters of these fibers in air and Ar were not almost observed. Thus, at the present time Hi-Nicalon-Type S will be best for the majority of CMC applications. Less

用于陶瓷基复合材料（CMC）增强纤维的三种类型的 SiC 纤维已上市；尼卡龙 (SiC_<1.34>O_<0.36>)、Hi-Nicalon (SiC_<1.39>0_<0.01>) 和 Hi-Nicalon-S 型 (SiC_<1.05>)。第一种纤维含有非晶碳氧化硅 (SiC_XO_Y) 相，下一种纤维是低氧微晶纤维，最后一种是接近化学计量的烧结 SiC 纤维。这种氧含量和微观结构的差异可能极大地影响纤维在不同环境下的高温性能。在高和中等氧分压下，碳化硅纤维被被动氧化，生成的稳定二氧化硅膜可保护材料免遭进一步氧化。在低氧分压下，SiC纤维发生活性氧化，并形成气体产物，导致SiC纤维严重损坏。在目前的工作中，这些 SiC 纤维在 1773K 的 Ar-O_2 气体混合物中进行氧化，氧气分压 (po_2) 从 1 到 10^5 Pa，以研究主动到被动的氧化转变。对于Nicalon，活性氧化发生在po^2≤100Pa，对于Hi-Nicalon，发生在po^2≤10Pa，对于Hi-Nicalon-S型，活性氧化发生在po^2≤1Pa。po^2值取决于SiC_XO_Y相的量。另一方面，为了更好地了解高温 CMC 增强的可靠性，研究这些纤维的蠕变行为也很重要。在空气和氩气中，在 1573-1723 K 的温度下，施加 0.35-0.75 Gpa 的负载，对单丝进行拉伸蠕变测试。该蠕变装置最初是在科学研究补助金 ((B)(2)) 的支持下生产的。从空气和氩气中蠕变的应力指数和活化能值来看，Nicalon、Hi-Nicalon和Hi-Nicalon-Type S的蠕变变形机制分别与晶界扩散、晶界滑动和位错运动有关。几乎没有观察到这些纤维在空气和氩气中的蠕变参数之间的差异。因此，目前 Hi-Nicalon-Type S 最适合大多数 CMC 应用。较少的