分馏塔裂纹焊接钎料研制

分馏塔塔壁焊缝分段出现裂纹,裂纹长度约200mm,焊接需采用钎焊,钎焊技术要求高,钎料选型特殊,每次钎焊都要请外单位援助。为降低费用,自行研制焊接用钎料,试制结果表明:比购买钎料节约6万多元、比请外援节约4万多元;同时也培养、锻炼了职工自主创新的能力。     

金刚石刀具银钎焊方法

为了更好地实现金刚石刀头与刀具基体的连接,并保证一定的结合强度,采用银钎焊方法。银钎料的元素成分和含量、钎焊剂类型和作用、加热设备及感应器形状的选择和温度控制、焊缝尺寸大小和装配间隙、钎焊前的预处理等是获得优质钎焊接头的关键因素。通过对获得的银钎焊接头进行试验分析和公式应力计算及无损检测等金刚石刀具银钎焊方法的可靠性评估,结果达到并满足了金刚石刀具的切削强度要求。有效预防或避免了钎焊接头的缺陷产生,从而获得了优质的钎焊接头,保证并延长金刚石刀具的使用寿命。     

Wetting behavior and brazing of titanium-coated SiC ceramics using Sn0.3Ag0.7Cu filler

By coating active titanium, Sn0.3Ag0.7Cu (SAC) filler wetted SiC effectively, as the contact angle decreased significantly from ~145° to ~10°. Ti₃SiC₂ and TiO_x (x ≤ 1) reaction layers were formed at the droplet/SiC interface, leading to the reduction of contact angle. Reliable brazing of SiC was achieved using titanium deposition at 900°C for 10 minutes, and the typical interfacial microstructure of Ti-coated SiC/SAC was SiC/TiO_x + Ti₃SiC₂/Sn(s,s). Comparing to direct brazing, Ti–Sn compounds in the brazing seam were effectively reduced and the mechanical property of joints was dramatically improved by titanium coating. The optimal average shear strength of SiC joints reached 25.3 MPa using titanium coating- assisted brazing, which was ∼62% higher than that of SiC brazed joints using SAC-Ti filler directly.     

钎焊金刚石工具钻孔加工工程陶瓷的扭矩研究

文章采用钎焊法制备出三种不同粒度的金刚石钻孔工具,并对工程陶瓷材料SiC和Al2O3进行孔加工实验,分析在不同的主轴转速、进给速度以及冷却液的种类和浓度的条件下钎焊工具扭矩的变化。结果表明:扭矩随着主轴转速和进给速度的增加而增大,且随着金刚石粒度的增大而相应增加。扭矩随着冷却液Op10和十六烷基三甲基溴化氨浓度的增加而相应减小,且都小于水冷却,其中加入十六烷基三甲基溴化氨冷却液产生的扭矩最小。     

钎焊金刚石／cBN砂轮基体工艺方法初探

针对目前国内制作钎焊金刚石／cBN砂轮的几种工艺方法,分析了其中存在的优缺点。根据工厂试验中出现的实际问题：焊接的温度对砂轮基体硬度影响较大,进而影响了对精度的保持,文章指出了寻找合适基体材料的方法。为解决高温钎焊对基体的影响提供了一个较好的样本。要满足cBN／金刚石砂轮基体的力学性能需要,建议砂轮基体采用40Mn2这种材料,在700℃左右回火,其硬度可以达到HRC38左右,能够满足高速磨削和高精度磨削的要求。     

Microstructure evolution and bonding strength of the Al2O3/Al2O3 interface brazed via Ni-Ti intermetallic phases

In this study, Al₂O₃ workpieces were vacuum brazed by using Ni-45Ti binary alloy. The interfacial microstructure evolution of the joints obtained at different brazing temperatures was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The bonding strength of the joints was measured by shear testing. The results indicated that Ni₂Ti₄O and AlNi₂Ti were the main reaction products in the joint areas. Moreover, the Ti₂Ni intermetallic compound formed in the brazing seam. The typical layer structure of the brazed joints was Al₂O₃/AlNi₂Ti/Ni₂Ti₄O/Ti₂Ni + NiTi/Ni₂Ti₄O/AlNi₂Ti/Al₂O₃. With the brazing temperature increasing, the thickness of the Ni₂Ti₄O reaction layer adjacent to the Al₂O₃ substrate increased significantly, while the AlNi₂Ti phase had a tendency to dissolve with the brazing temperature increasing. The mechanism for the microstructure evolution was also discussed. The maximum shear strength of 125.63±4.87 MPa of the joints was obtained when brazed at 1350 °C for 30min. The fracture occurred hardly in the interface between Al₂O₃ and Ni-45Ti filler alloy.     

Reactive wetting behavior and mechanism of AlN ceramic by CuNi-Xwt%Ti active filler metal

In order to propel the application of the developed CuNi-Xwt%Ti active filler metal in AlN brazing and get the universal reactive wetting mechanism between liquid metal and solid ceramic, the reactive wetting behavior and mechanism of AlN ceramic by CuNi-Xwt%Ti active filler metal were investigated. The results indicate that, with the increasing Ti content, surface tension for liquid CuNi-Xwt%Ti filler metal increases at low-temperature interval, but very similar at high-temperature interval, which influence the wetting behavior on AlN ceramic obviously. CuNi/AlN is the typical non-reactive wetting system, the wetting process including rapid wetting stage and stable stage. The wettability is depended on surface tension of the liquid CuNi filler metal completely. However, the wetting process of CuNi-8wt.%Ti/AlN and CuNi-16 wt%Ti/AlN reactive wetting system is composed by three stages, which are rapid wetting stage decided by surface tension, slow wetting stage caused by interfacial reaction and stable stage. For CuNi-8wt.%Ti/AlN and CuNi-16 wt%Ti/AlN reactive wetting system, although the surface tension of liquid filler metal is the only factor to influence the instant wetting angle θ₀ at rapid wetting stage, the reduced free energy caused by interfacial reaction at slow wetting stage plays the decisive role in influencing the final wettability.     

Al_2O_3/Cu_(70)Ti_(25)Zr_5/Nb界面结构及强度

本研究选用Cu70 Ti2 5 Zr5 活性钎料钎焊Al2 O3/Nb .通过对Al2 O3/Cu70 Ti2 5 Zr5 /Nb界面结构及接头性能研究 ,旨在进一步揭示Al2 O3/含Ti活性钎料间界面反应机制 ,并为指导工程应用提供最佳工艺参数 .借助扫描电镜、能谱、X射线衍射探讨了Al2 O3/Cu70 Ti2 5 Zr5 /Nb钎焊接头界面结构 ,并采用拉剪试验评价了接头强度 .研究结果表明 ,时间 0 .6ks ,温度小于 12 2 3K ,界面产生了 3种新相 :Cu2 Ti4O ,Ti0 .5 Zr0 .5 O0 .1 9,CuTi,界面结构为Al2 O3/Cu2 Ti4O +Ti0 .5 Zr0 .5 O0 .1 9/CuTi/Cu固溶体 +CuTi;温度大于 12 93K ,界面产生了Cu2 Ti4O ,Ti,CuTi 3种新相 ,界面结构为Al2 O3/Cu2 Ti4O/Ti固溶体 /CuTi/Cu固溶体 +CuTi.在 12 93K ,0 .6ks条件下 ,接头剪切强度最高达到 162MPa ,温度大于或小于12 93K ,强度下降     

Microstructure and joining strength evaluation of SiC/SiC joints brazed with SiCp/Ag–Cu–Ti hybrid tapes

SiC particulates were mixed with Ag–Cu–Ti powders to fabricate SiC_P/Ag–Cu–Ti (SICACT) sheets by tape casting process, which were used to braze the sintered SiC ceramics with the structure of SiC/Ag–Cu–Ti foil/SICACT sheet/Ag–Cu–Ti foil/SiC. Microstructure and joining strength both at room temperature and at high temperature were characterized by electron probe X-ray microanalyzer, electron dispersive spectroscopy, transmission electron microscopy, and flexural strength test. The SiC particulates from the SICACT sheets were randomly distributed in the filler alloy matrix and reacted with Ti from the filler alloy. Reaction products TiC and Ti₅Si₃ were found in the interfacial reaction layer. With the increase in SiC particulates volume fraction, the joining strength at room temperature first increased, and then decreased, which was affected by both CTE mismatch and the thickness of the reaction layer. In addition, the joining strength of joints brazed using SICACT sheets at 600?°C can reach 197 MPa, which was obviously higher than that brazed using Ag–Cu–Ti filler alloy.     

Wettability and interfacial phenomena in the liquid-phase bonding of refractory diboride ceramics: Recent developments

Joining and integration technologies are integral to manufacturing of components based on ultrahigh-temperature ceramics (UHTCs) such as transition metal diborides. Brazing is a particularly attractive joining technique because of its simplicity and versatility, but its use to join the UHTCs demands knowledge of the complex interplay among high-temperature wettability, interfacial reactions, and chemical and thermoelastic compatibilities. This paper summarizes the research and development activities carried out over the last two decades to characterize the wettability and interfacial phenomena in brazing of refractory diboride ceramics. The contact angle data of various metal alloys on diboride-based ceramics have been collected and critically evaluated in conjunction with an analysis of the chemistry and structure of the interface to understand the underlying mechanisms and phenomena that govern interface formation. It explores how solid–liquid interactions impact and are impacted by physical, chemical, and mechanical properties of joined materials. It also describes how this knowledge has been successfully utilized to create liquid-phase bonded diboride-based joints. The paper concludes with a summary of the current state of the art and highlights integration challenges and future research and technology development needs in the area.