SiC-Glass涂层碳/碳复合材料的中低温氧化行为及机制研究

为揭示具有良好高温(1300～1600 ℃)抗氧化性能的SiC-Glass涂层在中低温(500～1200 ℃)条件下的氧化防护性能,对SiC-Glass涂层碳/碳(C/C)复合材料的中低温氧化行为和机制进行了系统研究.结果表明,SiC-Glass涂层C/C复合材料的中低温氧化失重服从直线规律,但氧化机制存在温度依赖性,可分为2个区段:(1) 低温区(500～800 ℃),氧化失重速率与温度服从Arrhenius关系,氧化主要受控于氧在涂层缺陷内的扩散速率;(2) 在中温区(800～1200 ℃),氧化失重速率与温度不服从Arrhenius关系,氧化过程受氧在涂层缺陷中的扩散、SiC内涂层材料的氧化、Glass外涂层的部分熔融愈合等多种因素联合控制.对比分析表明,SiC-Glass涂层的中低温抗氧化性能不及其高温抗氧化性能优异.中低温下,涂层缺陷愈合不充分是导致这一现象的主要原因.

Oxidation Behaviour and Mechanism of SiC-Glass Coated Carbon/Carbon Composites at Low-and Medium-Temperature

In present work, the oxidation behavior and oxidation mechanism of SiC-Glass multi-layer coating, exhibiting good oxidation resistance at high temperature (1300～1600 ℃), were investigated in air at low- and medium-temperature (500～1200 ℃), which was aimed to reveal the anti-oxidation property and oxidation reason of the SiC-Glass coating at the temperature below 1300 ℃. The results indicated that the isothermal oxidation behavior of coated carbon/carbon (C/C) samples always exhibited a linear weight-loss rule at the temperature between 500℃ and 1200℃. Temperature dependence of oxidation mechanism was found during the oxidation tests. The oxidation process of SiC-Glass coated C/C composites could be divided into two stages: (1) at low temperature (500～800 ℃), an Arrhenius relationship was found between oxidation rate and temperature, and the oxidation was controlled by the oxygen diffusion in the coating defects; (2) at medium temperature (800～1200 ℃), the oxidation was limited synchronously by several factors, including oxygen diffusion in coating defects, constituent oxidation of SiC inner layer and partial coating defect healing of Glass outer layer. Therefore, no Arrhenius relationship was present between the oxidation rate and the temperature. Additionally, it was found that the oxidation resistance of SiC-Glass coating at 500～1200 ℃ was not as good as that at 1300～1600 ℃, which was due to incomplete healing of coating defects at the temperature below 1200 ℃.