TiC金属陶瓷与304不锈钢的连接工艺及相关理论研究

发布时间：2018-04-16 11:26

本文选题：TiC金属陶瓷 + 钎焊　；参考：《重庆大学》2016年博士论文

【摘要】：TiC金属陶瓷具有高硬度、高耐磨、耐高温、抗氧化等特性,从而得到了普遍的重视和广泛的应用。但TiC金属陶瓷的耐冲击性低、机械加工性差,极大限制了它的应用。将其与其他金属材料(如钢)连接成复合构件将进一步扩大其在工程中的应用范围。但TiC金属陶瓷与金属的物理、化学、力学性能差异极大,很难得到理想的连接界面,且接头中容易产生的残余应力和较多的连接缺陷。因此,研究TiC金属陶瓷与金属的连接具有重要的实际意义。本文针对TiC金属陶瓷与钢的连接问题,开展了TiC金属陶瓷/304不锈钢(304SS)的钎焊、固相扩散连接与部分瞬间液相连接研究工作。目前,陶瓷与金属的焊接或连接多采用Ag-Cu基合金作为填充层,其中贵金属Ag的含量大多大于50%,导致连接成本高,不便于工业生产的广泛应用。另外,多数Ag-Cu基钎料连接的接头服役温度较低,大约500℃甚至低于500℃,使陶瓷在高温结构件上的使用受到限制。因此,有待开发新型低成本、高性能的钎料。以Cu作为活性钎料的基础成分,依据键参数理论与吉布斯自由能的计算,选择添加Ni、Mn和Nb元素作为Cu基活性钎料的组元,对TiC金属陶瓷与304SS进行了钎焊试验。通过SEM、EDS和XRD等方法,研究了活性元素Nb的含量、工艺参数对TiC/CuNi MnNb/304SS钎焊界面微观结构与性能的变化规律。分析发现,活性元素Nb与TiC发生化学反应,生成具有一定金属性和陶瓷性的NbxCy化合物,对界面的物理化学性质起到了过渡作用,界面结构为304SS/σ/Cus.s/Nb6C5/Nb2C/αTi/TiC,揭示了CuNiMnNb合金钎料钎焊TiC/304SS的界面形成机制。Nb的含量、钎焊温度和保温时间直接影响界面结合强度,当Nb含量8wt%、钎焊温度1170℃、保温时间15min时,TiC/Cu52Ni32Mn8Nb8/304SS接头的剪切强度高达92.5MPa。钎焊接头的服役温度一般在钎料熔化温度以下,受钎料的熔点限制,而固相扩散连接接头相比钎焊接头,其服役温度受中间层熔点的影响较小,所以广受关注。固相扩散连接中,由于TiC金属陶瓷与304SS的热膨胀系数差别很大,在接合面附近将形成高的残余应力,降低这种残余应力的中间层选择是实现可靠连接的关键。采用Ti-Nb-Cu中间层,在连接温度925℃、保温时间20min、连接压力8MPa条件下,固相扩散连接的TiC/304SS接头的平均剪切强度为84.6MPa。剪切断裂发生在近TiC/Ti连接界面的TiC金属陶瓷内部。分析发现,TiC金属陶瓷与中间层Ti之间形成连续的Ti原子过渡。Nb与Ti无限固溶,并且Nb的线膨胀系数与TiC金属陶瓷极为接近,在接头中可形成应力缓冲区。Cu延展性很好,并且与304SS中的Fe、Cr等元素反应不生成金属间化合物,有利于接头性能的提高。TiC/Ti-Nb-Cu/304SS恒压固相扩散连接的时间长、压力大,在此基础上为了促进原子间的互扩散,缩短连接时间,而引入了脉冲加压技术。试验将中间层调整为Ti-Nb,连接温度降低至890℃,保温时间缩短至4~16min,对TiC/304SS进行恒压(10MPa)与脉冲加压(2~10MPa)扩散连接对比实验。通过对接头中原子扩散系数的理论计算发现,脉冲压力确实有效的提高了原子的扩散速度。当保温时间仅为10min时,接头的平均剪切强度已高达110 MPa,说明采用脉冲加压扩散连接技术不仅大幅度提高了连接效率,而且提高了连接接头的力学性能。该接头的断口呈混合型断裂的特征,即裂纹沿着TiC金属陶瓷与界面反应区间交替扩展,这种断裂方式消耗的能量更多,对应的接头强度更高,从而揭示了脉冲压力对接头性能的影响规律。固相扩散连接工艺对待焊母材端面的粗糙度要求很高,而部分瞬间液相连接(PTLP)克服了这些缺点,并一定程度上综合了钎焊与固相扩散连接的优点。采用Ti-Cu-Nb金属中间层,对TiC金属陶瓷与304SS进行了PTLP连接试验。在TiC金属陶瓷一侧,Ti-Cu层在高于共晶点的连接温度下熔化,与TiC金属陶瓷、核心金属层Nb产生界面反应;而在304SS一侧,Nb与304SS进行固相扩散,以形成具有固相扩散特征的连接结构。在连接温度890℃、保温时间10min、连接压力10MPa条件下,TiC/Ti-Cu-Nb/304SS接头剪切强度最高达106.7MPa,界面结构为304SS/σ/Nb/Cu Ti/CuTi2/αTi/TiC。通过Ti-Cu化合物形成规律的理论计算,以及对PTLP工艺参数的优化,为界面产物的生长控制提供理论依据。通过上述研究表明,选择合适的连接工艺可以实现TiC金属陶瓷与304SS的高强度连接。而合理的钎料/中间层设计、工艺参数的优化,可促进接头中原子的扩散与冶金反应,从而实现高效率、低成本、高性能的连接,为TiC金属陶瓷与异种材料的连接提供新的思路。
[Abstract]:TiC cermet has high hardness, high wear resistance, high temperature resistance, antioxidant properties, which has been widely used. But TiC metal ceramic impact resistance low, poor machinability, greatly limits its application. Compared with other metal materials (such as steel) with composite component it will further expand its scope of application in engineering physics. But, TiC metal ceramics and metal chemical, mechanical properties vary greatly, it is difficult to get ideal interface, and easy to produce residual force and more defects should be connected. Therefore, it has important practical significance to study TiC metal ceramic and metal connection according to the connection problems. TiC metal ceramics and steel, the TiC metal ceramic /304 stainless steel (304SS) brazed connection work connected with partial transient liquid diffusion in solid phase. At present, or even the welding of ceramics and metals The use of Ag-Cu alloy as filler layer, the content of noble metal Ag are greater than 50%, leading to the connection of high cost, not easy to widely used in industrial production. In addition, the joint most Ag-Cu based solder connection service temperature is low, about 500 C or less than 500 degrees, the ceramic used in high temperature structural parts Limited. Therefore, to develop a new type of low cost and high performance. The solder is based on Cu component of active filler, according to bond parameter theory and calculation of the Gibbs free energy, choose to add Ni, Mn and Nb elements as Cu based active filler metal element, the brazing of TiC ceramic metal and 304SS by SEM, EDS and XRD, the content of the active element Nb, variation of process parameters on the microstructure and properties of TiC/CuNi MnNb/304SS solder interface. Analysis shows that the active element Nb and TiC in chemical reaction, generate out NbxCy compound metal and ceramics, physical and chemical properties of the interface plays a role in the transition, the interface structure of 304SS/ alpha Sigma /Cus.s/Nb6C5/Nb2C/ Ti/TiC, reveals the content of brazing of CuNiMnNb alloy TiC/304SS the interface formation mechanism of.Nb, the brazing temperature and holding time directly affects the interfacial bonding strength, when the content of Nb 8wt%. The brazing temperature is 1170 degrees centigrade, holding time 15min, the service temperature of the shear strength of TiC/Cu52Ni32Mn8Nb8/304SS joints of 92.5MPa. solder joint is usually below melting temperature, the melting point of the solder, and solid phase diffusion bonding joint in soldered joints, the service temperature is affected by the middle layer of the lower melting point, so wide attention. The solid phase diffusion bonding because, TiC metal ceramic and 304SS thermal expansion coefficient difference is very big, in the engagement near the surface will form the high residual stress, reduce the residual Selection of interlayer stress is the key to realize the reliable connection. The Ti-Nb-Cu connection in the middle layer, 925 degrees Celsius temperature, holding time 20min, connect the pressure under the condition of 8MPa, the average shear strength of solid diffusion TiC/304SS connections of the 84.6MPa. shear fracture occurs near the TiC/Ti connection interface of TiC cermet. Internal analysis found that continuous Ti atomic transition.Nb and Ti solid solution is formed between TiC cermets and the middle layer of Ti, Nb and TiC and the linear expansion coefficient of metal ceramic is very close to the formation of stress buffer.Cu good ductility in the joint, and with 304SS in Fe, Cr and other elements do not generate reaction intermetallic compound can improve mechanical performance of.TiC/Ti-Nb-Cu/304SS constant pressure solid phase diffusion bonding time, pressure, on this basis, in order to promote inter diffusion, shorten the connection time, and introduces the pulse compression technology Test operation. The middle layer is adjusted to Ti-Nb, connect the temperature is reduced to 890 DEG C, the holding time shortened to 4~16min, the constant pressure of TiC/304SS (10MPa) and pulse pressure (2~10MPa) diffusion bonding experiments. Based on atomic diffusion coefficient in the joint theory calculations show that the pulse pressure does effectively improve the diffusion velocity of atom when the holding time is only 10min, the average shear strength of the joint has been as high as 110 MPa, the pulse pressure diffusion bonding technology not only greatly improved the efficiency, but also improve the mechanical properties of joints. The fracture of the joint is characteristic of mixed fracture, the crack along the TiC metal ceramic and interfacial reaction alternate interval extension, the fracture mode of more energy consumption, the joint strength corresponding to the higher, which reveals the influence of pulse pressure on mechanical properties of solid state diffusion bonding process on. The welding surface roughness is high, and the partial transient liquid phase bonding (PTLP) overcomes these shortcomings, and to a certain extent, the brazing and solid phase diffusion bonding. The advantages of using Ti-Cu-Nb metal intermediate layer, the PTLP connection test of TiC metal ceramic and 304SS. On the side of the TiC ceramic and metal. Connect the temperature above the eutectic point in Ti-Cu layer, and TiC metal ceramic, metal core layer Nb interfacial reaction; while in the side of 304SS, Nb and 304SS solid phase diffusion, and is formed by the connection structure. The solid phase diffusion characteristics in connection with 890 degrees Celsius temperature, holding time 10min, connect the pressure under the condition of 10MPa. The shear strength of TiC/Ti-Cu-Nb/304SS joints up to 106.7MPa, the calculation of interface structure of 304SS/ /Nb/Cu Ti/CuTi2/ Ti/TiC. formation of alpha sigma compounds by Ti-Cu theory, and the optimization of PTLP parameters, for the growth of the product interface Control provides a theoretical basis. Through the above study, select the appropriate high strength connection technology can achieve TiC cermets and 304SS connection. The solder / middle layer and reasonable design, optimization of process parameters, can promote the diffusion and reaction in metallurgical joint atoms, so as to realize the high efficiency, low cost, high performance connection and provide new ideas for the connection of TiC cermet with dissimilar materials.

【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG40;TQ174.6

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