SiC陶瓷与Ni基高温合金连接件应力的有限元分析

Finite element analysis for welding stress of SiC ceramic to Ni-based superalloy joints

陶瓷与金属连接具有重要的工程应用背景,然而却面临诸多技术难关,连接件的热应力缓解便是其中之一。本文作者采用弹性有限元方法,对采用不同材料作为中间层得到的实际连接尺寸的SiC陶瓷与Ni基高温合金连接件的应力进行计算,并结合各种材料的塑性对连接件的应力进行定性分析。计算结果表明,SiC陶瓷与Ni基高温合金直接连接产生的热应力很大。最大轴向拉应力位于陶瓷近缝区,导致连接件强度偏低或断裂。采用功能梯度中间层或软金属中间层能在一定程度上缓解热应力;硬金属中间层虽然不能缓解应力,但能改善应力分布状态,使最大轴向拉应力迁移出比较薄弱的陶瓷一侧,有利于连接强度的提高;采用软、硬金属复合中间层具有较好的缓解应力和改善应力分布的效果,但却较多地增加了连接件的界面,有可能导致负面效应,在实际工程应用中需要根据具体情况,权衡利弊,综合考虑。

The joining of ceramics to metals is of importance to extend the engineering application of the materials.It,however,is faced with a number of technical difficulties,one of which is the relaxation of the thermal stress of joints.The elastic finite element analysis shows that the direct joining of SiC ceramic to Ni-based superalloy generates large thermal stress.The maximum axial tensile stress is located within the ceramic near the weld seam,which leads to low strength or breaking of the joints.The utilizing of functionally gradient interlayer or soft metal interlayer can relax the thermal stress of joints to a certain extent.Although the utilizing of hard metal interlayer can not relax the thermal stress of joints,it can improve the distribution of the stress,leading to that the maximum axial tensile stress migrates out of the ceramic,which is weak under tensile stress.This contributes to improve the strength of joints.The utilizing of multiple interlayers composed of soft alternating with hard metal interlayers can produce the above-mentioned two positive effects,but it generates more interfaces in the joints,which may produce negative effects.So it is needed to consider comprehensively and to take balance in practical engineering applications.