基于表面活化的陶瓷/金属钎焊连接机理及工艺研究

Based on the requirement of interfacial reaction control and process improvement of brazing ceramic and metal, a method to enhance the brazing quality between ceramic and metal by surface activation is proposed. The method utilizes plasma irradiation and deposition of bonding surfaces to remove contaminations such as adsorption layer and oxide prior to brazing. It can avoid the adverse effects of contaminations on the brazing process and joint properties, promote the wetting of brazing fillers and significantly improve the interfacial microstructure and joining quality. The project focuses on the surface activation and interfacial reaction. The effects of surface activation on the composition, microstructure and stress state of bonding surfaces are investigated in detail and the activation mechanism is clarified. The wetting and spreading behavior of brazing filler on activated ceramic and metal surfaces is systematically studied, and the influence of surface activation on wettability is revealed. According to the optimization of brazing process and characterization of interfacial microstructure, the reaction model of each interface is established and the evolution of interfacial microstructure is clarified. Moreover, the relationship between the surface reaction products and the joint properties is determined. Furthermore, the influence of surface activation on the interfacial microstructure and properties of brazed joints is revealed, and the mechanism of surface activation brazing is clarified. The project aims to develop surface activation brazing technology, also provides new ideas for joining ceramic and metal, meanwhile promotes the application of surface technology in the field of materials joining and also promotes the development of ceramic-metal joining technology.

本项目针对陶瓷与金属钎焊界面反应控制和工艺改进的需求，提出了利用表面活化提高陶瓷与金属钎焊质量的方法。利用离子轰击及表面沉积技术对陶瓷及金属表面进行活化并实现其高质量钎焊连接，避免表面吸附层、氧化膜等对钎焊工艺及接头质量的不利影响；促进钎料润湿，改善接头界面结构及性能。本项目以表面活化和界面反应为切入点，重点研究表面活化对陶瓷及金属表面成分、微结构、应力状态等的影响，揭示活化机理；系统研究钎料在活化的陶瓷和金属表面的润湿铺展行为，阐明表面活化对润湿性的影响规律；基于钎焊工艺优化及界面结构表征，建立接头内各界面的反应模型，阐明接头界面组织演化规律，确定界面反应产物与连接性能的对应关系，揭示表面活化对接头界面组织结构及性能的影响规律，阐明表面活化钎焊连接机理。本项目旨在开发表面活化钎焊技术，为陶瓷与金属的连接提供新思路，同时推广表面技术在连接领域的应用，促进陶瓷与金属连接技术的发展。

针对陶瓷与金属钎焊界面反应控制和工艺改进的需求，提出了利用Ar离子轰击活化提高SiC陶瓷与铝合金钎焊质量的方法。利用离子轰击技术对陶瓷及金属表面进行活化并实现其高质量钎焊连接，避免表面吸附层、氧化膜等对钎焊工艺及接头质量的不利影响；促进钎料润湿，改善接头界面结构及性能。基于本项目的研究，为陶瓷与金属的连接提供了新思路，促进了陶瓷与金属连接技术的发展。. Ar离子轰击能致使SiC表面的Si-C键断裂，首先形成SiCx(x<1)、C间隙原子和空位；随着离子轰击的持续进行，SiCx(x<1)中Si-C键继续发生断裂，最终形成大量的C和Si间隙原子、空位以及一部分反占位缺陷，从而在SiC表层形成非晶层。离子轰击使SiC表面能提高，从而使初始润湿角下降；同时会加速AgCu-Ti钎料中的Ti和母材之间的界面反应，孕育期大幅缩短；但离子轰击导致的SiC表面非晶层会阻碍Ti原子的扩散，从而轰击处理SiC润湿试样的缓慢铺展或平衡阶段过程耗时增加，最终钎料在不同剂量或偏压轰击SiC陶瓷表面的润湿角趋于一致。经离子轰击预处理后，其接头界面反应层生成是基于一步化学反应：6Ti + 3(Si ) + (C) = TiC + Ti5Si3，∆G(T) = -787.3 + 22.1 × 10^-3 T (kJ ⁄mol)。. Ar离子轰击可有效地消除铝合金基体表面的氧化膜，并改变基体表面组织及应力分布状态，另外镀Cu层与离子轰击后的基体表面之间紧密结合，且结合界面存在着原子扩散过渡层，最终实现了铝合金的基体表面活化。当钎焊温度为600°C时，镀Cu层厚度分别为20μm和5μm的表面活化辅助钎焊接头均达到最大剪切强度42.2MPa和50.7MPa，但钎焊温度升高到610°C时，钎焊接头中因存在异常粗大的晶粒而导致接头剪切强度急剧下降。因此钎焊温度的提高一方面增大接头成分均匀化程度，有利于接头力学性能的提高；另一方面则会导致接头晶粒逐渐长大粗化，不利于接头的力学性能。在钎焊过程中，Al-Cu共晶液相的晶界渗透现象导致晶界的结合强度减弱，基体晶粒沿晶界剥落进入共晶液相中并逐渐溶解。