Ti含量对Ni-14Cr-10P-xTi焊膏连接C/C复合材料组织及性能的影响

将不同质量分数的钛粉加入Ni-14Cr-10P合金粉末中,再配合高分子聚合物制得膏状Ni-14Cr-10P-x Ti活性钎料,用制得的焊膏钎焊C/C复合材料,然后测试了钎焊接头的剪切强度,通过扫描电子显微镜、能谱分析仪、电子探针显微分析仪等对钎焊接头界面组织特征进行分析。结果表明:活性元素Cr、Ti与C/C复合材料表面的C反应而起到表面改性的作用,使得钎料能在C/C复合材料表面润湿、填缝。随着Ti元素加入量的增加,钎焊接头剪切强度先增加再降低。Ti质量分数为1%时,TiC呈颗粒状弥散分布,使得钎料层强化,接头剪切强度增加;当Ti增加到3%时,在界面处形成了连续的Cr_3C_2/TiC脆性材料层,接头剪切强度下降;Ti质量分数达到5%时,Ti与Cr_3C_2反应使得梯度界面层消失,界面物质热膨胀系数差异增大,残余热应力增加,同时Ti与Ni、Cr形成的金属间化合物增加并集中分布在钎料层中,导致接头剪切强度急剧下降。

Effects of Ti Content on Microstructure and Properties of C/C Composites Brazed with Ni-14Cr-10P-xTi Pasty Filler Metal

The titanium powder was added into the Ni-14Cr-10P alloy powder, and the high-molecular polymer was mixed at high speed to obtain the paste-like Ni-Cr-P-Ti active filler metal. The C/C composites were brazed with the prepared pasty filler, and then the shear strength of the brazed joint was tested. The interfacial microstructure of the brazed joint was analyzed by scanning electron microscopy, energy spectrum analyzer, and electron probe microanalyzer. The results show that the active elements Cr and Ti react with C on the surface of the C/C composites to act as a surface modification, and thus, the brazing material can wet and fill the surface of the C/C composites. As the amount of Ti added increases, the shear strength of the brazed joint increases first and then decreases. When Ti content is 1%, TiC is dispersed in a granular form. The brazing layer is strengthened and the joint shear strength is increases. When Ti increases to 3%, a continuous Cr₃C₂/TiC brittle layer is formed at the interface, and the joint shear strength decreases. When Ti content reaches 5%, Ti reacts with Cr₃C₂ to make the gradient interface layer disappear. The thermal expansion coefficient of the interface material increases, leading to the increase of the residual thermal stress, and (Ni, Cr, Ti) intermetallic compounds increase and concentrate in the brazing layer. This causes a sharp drop in the shear strength of the joint.