辐照防护用TiC/C功能梯度材料微结构与残余热应力分析

Microstructure and Residual Stress of TiC/C Functionally Graded Materials for Irradiation Protection of Carbon-based Composites

为提高面向等离子体C基材料耐侵蚀性能,通过化学气相沉积工艺在碳/碳复合材料(C/C)表面制备了一系列TiC/C复合涂层。分别通过扫描电子显微镜(SEM)和X射线光电子能谱(XPS)表征了HT-7托卡马克中长脉冲等离子体放电后的不同涂层表面的微观结构和成分变化。结果表明,在富C的TiC/C涂层中观察到明显的侵蚀坑洞,但未发现裂纹。相反在纯TiC涂层中未观察到明显的侵蚀凹坑,但是观察到大的裂纹。基于这些结果,进一步设计制备了TiC/C功能梯度材料,并通过有限元计算了梯度材料内残余的热应力和变形,结果表明,引入TiC/C作为过渡层可显着降低材料内残余热应力,其最大值降低至474 MPa,同时变形程度大大降低,这有利于避免形成大的裂纹和杂质进入等离子体环境。

To improve the erosion resistance of carbon-based facing materials during plasma instabilities,a series of TiC/C composites were prepared on C/C substrates via chemical vapor deposition(CVD).Microstructure and composition of the samples after long pulse plasma discharge in HT-7 tokamak were characterized by using scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS).Distinct eroded pits were observed in the C-rich TiC/C coatings,but no cracks were present,On the contrary,the eroded pits were ambiguous in the case of pure TiC coating,but large cracks were observed.On the basis of these results,TiC/C functionally graded materials were further prepared,whose residual thermal stresses and deformation were then analyzed by using finite element calculation.It was found that the introduction of TiC/C composites as transition layer had significantly decreased the stress shifts,with the largest shift to as low as 474 MPa.Additionally,extent of deformation was largely decreased,This is beneficial to avoiding formation of large cracks and preventing impurities from entering plasma environment.