CVD-SiC反射镜制备过程中热应力变形的研究

采用CVD工艺在反应烧结碳化硅(RB-SiC)反射镜坯体上沉积了一层致密的碳化硅薄膜作为反射镜镜面.CVD-SiC和RB-SiC热物理性能上的差异引起的热残余应力和热变形,在很大程度上影响反射镜的质量,本文采用有限单元法计算了沉积过程中反射镜的温度场、应力场和热变形,采用X射线衍射方法测试了薄膜表面的残余应力.分析结果表明,薄膜存在较大的残余应力,包括热应力和本征应力,两者量值相当,热变形很小.

Thermal Stress and Displacement in Process of Producing CVD- SiC Mirror

The compact SiC film was deposited on the reaction bonded silicon carbon (RB -SiC ) mirror by chemical vapor deposition (CVD) process. Because of the difference of thermo-physical properties between CVD - SiC and RB - SiC, thermal residual stress and thermal displacement appeared. This would affect the quality of the mirror to a large extent. In this paper, temperature field, stress field and thermal displacement of the mirror were analyzed by finite element method in the course of deposition process. The residual stress of the CVD - SiC film surface was tested by X-ray diffraction method. Results show there is a larger residual stress in the film. Residual stress is comprised of thermal stress and essential stress, and their magnitude is equivalent. Thermal displacement of mirror surface is small.