Lifetime-applied stress response in air of a SiC-based Nicalon-fiber-reinforced composite with a carbon interfacial layer:: Effects of temperature (300° to 1150°C)
Lifetime-applied stress response in air of a SiC-based Nicalon-fiber-reinforced composite with a carbon interfacial layer:: Effects of temperature (300° to 1150°C)
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DOI：
10.1111/j.1151-2916.1998.tb02567.x
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发表时间：
1998-07-01
影响因子：
3.9
通讯作者：
More, KL
中科院分区：
文献类型：
--
作者：
Becher, PF;Lin, HT;More, KL
描述了具有类似于0.3 μ m厚碳界面层的Si-O-C基（Nicalon）纤维平纹织物增强SiC-基质复合材料（类似于7%闭孔）在空气中的寿命作为所施加的挠曲应力和温度（300-1150 ℃）的函数。具有和不具有外部SiC密封涂层的两个样品的测量寿命是相似的，并且随着施加的弯曲应力（对于大于-90 MPa的应力）和温度而降低。在大于或等于600摄氏度的温度下，外部CVD SiC涂层对寿命的影响可以忽略不计;然而，在425摄氏度下，使用外部SiC涂层观察到寿命的可检测的改善。当所施加的应力降低到明显的“阈值应力”（例如，对于在小于或等于950 ℃的温度下进行的测试，在大于或等于1000小时的时间内没有观察到失效。电子显微镜观察表明，在425 ℃和600 ℃的测试期间，界面碳层逐渐被去除。在这些情况下，失效与纤维失效和拔出有关。在950 ℃和1150 ℃时，由于Nicalon纤维和SiC基质的氧化，碳界面层被消除并被厚的二氧化硅层取代。这导致复合材料脆化。
The lifetimes in air as a function of applied flexure stress and temperature (300-1150 degrees C) are described for a Si-O-C based (Nicalon) fiber plain-weave cloth reinforced SiC-matrix composite (similar to 7% closed porosity) with an similar to 0.3 mu m thick carbon interfacial layer. The measured lifetimes of both samples with and without an external SiC seal coating were similar and decreased with applied flexural stress (for stresses greater than -90 MPa) and with temperature. At temperatures of greater than or equal to 600 degrees C, the external CVD SIC coating had negligible effect on the lifetimes; however, at 425 degrees C, a detectable improvement in the lifetime was observed with an external SiC coating. When the applied stress was decreased below an apparent "threshold stress" (e.g., similar to 90 MPa) for tests conducted at temperatures less than or equal to 950 degrees C, no failures were observed for times of greater than or equal to 1000 h, Electron microscopy observations show that the interfacial carbon layer is progressively removed during tests at 425 degrees and 600 degrees C, In these cases, failure is associated with fiber failure and pullout. At 950 degrees and 1150 degrees C, the carbon interface layer is eliminated and replaced by a thick silica layer due to the oxidation of the Nicalon fiber and the SiC matrix. This results in embrittling the composite.