垂直取向石墨烯包覆泡沫镍复合中间层钎焊C/C复合材料与Nb的工艺及性能

Process and properties of vertically aligned graphene coated Ni foam composite interlayer for brazing C/C composite and Nb

针对碳/碳(C/C)复合材料与铌(Nb)钎焊接头高残余应力问题及高温服役需求,采用等离子体增强化学气相沉积(plasma enhanced chemical vapor deposition,PECVD)方法获得了垂直取向石墨烯(vertically aligned few-layer graphene,VFG)包覆泡沫镍复合中间层,并使用该复合中间层搭配TiNi钎料辅助钎焊C/C复合材料与Nb.采用扫描电子显微镜、透射电子显微镜、X射线光电子能谱、拉曼光谱方法表征VFG及接头的微观组织结构及表面化学状态.结果表明,钎缝中原位形成了弥散分布的(Ti,Nb)2Ni颗粒及(Ti,Nb)C环状第二相,有效降低了钎缝整体的线膨胀系数,缓解了接头残余应力.同时,均匀分布的Nb(s.s.)使得钎缝组织保持了良好的高温塑性,接头在1000℃下的抗剪强度达到33 MPa,比无中间层直接钎焊接头的抗剪强度提高了450%.

To address the problem of high residual stresses and high-temperature service requirements in the brazed joints of carbon/carbon(C/C)composites and niobium(Nb),vertically aligned few-layer graphene(VFG)coupled with the TiNi solder were used during the brazing process.VFG was prepared by plasma enhanced chemical vapor deposition(PECVD)method in this study.The microstructure and the chemical state of the surface of the VFG and the joint were characterized by scanning electron microscopy,transmission electron microscopy,X-ray photoelectron spectroscopy,and Raman spectroscopy.Results revealed that the in-situ and uniform distribution of(Ti,Nb)2Ni particles and annular(Ti,Nb)C phases in the joint seam,effectively reduced the coefficient of thermal expansion of the joint seam and relieved the residual stresses in the joint.Meanwhile,the evenly distributed Nb solid solution endowed sound plasticity at high temperature to the joint seam.The shear strength of the joint at 1000℃reached 33 MPa,which is 450%higher than the directly brazed joint without interlayer.