In situ investigation of the pore development during reactive air brazing of aluminium oxide ceramics

氧化铝陶瓷反应空气钎焊过程中气孔形成的原位研究

• 批准号: 393030180
• 负责人: Professor Dr.-Ing. Wolfgang Tillmann
• 金额: --
• 依托单位: Lehrstuhl für Werkstofftechnologie (LWT)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/393030180?language=en
• 关键词: situ; investigation; pore; development; during

The aim of the research project is the fundamental investigation of RAB brazing processes, which lead to porous defects in the brazing joints. With the gained knowledge, a reduction of the porosity of RAB brazed components is aimed. For this, the high speed X-ray radiation technique is used for the first time as an examination method for in situ analyses of the material flow in high temperature brazing applications. The existing X-ray radiation system is adapted for this purpose to the requirements of high temperature brazing. This new examination method enables to identify the occurring temperature-dependent processes of the movements in the brazing gap with non-destructive in situ observation methods without the limitations of optical light examination processes. The high speed X-ray radiation further allows to analyze the boundary layers that were wetted at different times during the brazing process. The different areas that were identified are selectively analyzed metallographically and strength examinations are conducted, whereby the relations between different local pore structures, reaction layers, structures, and resulting strengths can be correlated with the material dynamics during the brazing process. In addition to the in situ examination of the material movements in the brazing gap, high-speed X-ray radiation offers the possibility to analyze the wetting attempts in an unprecedented quality. The temporal high-resolution observation of open wetting samples inside view allows an exact determination of the wetting angle at any temperature and dwell time. Problems of the depth of field, as known from optical hot-stage-microscopy, do not occur. A combined examination of the propagation velocity in open wetting attempts, in brazing gaps with different width, and at different temperatures will determine the influence of the wettability, the brazing temperature, and the gap width on the propagation velocity, pore size, and pore density. These cognitions lead to an improved understanding of the development of porous defects in RAB brazed ceramic composites.By in situ observation of the pore formation fundamental knowledge about their behavior in dependence of the influencing factors is expected. So far, it was technically not possible to conduct in situ analyzes during the brazing process. A transfer of the gained knowledge even on other brazing processes and material groups can contribute to an increase in the tightness and service life of RAB brazed components.

该研究项目的目的是对 RAB 钎焊工艺进行基础研究，该工艺会导致钎焊接头中出现多孔缺陷。根据所获得的知识，我们的目标是降低 RAB 钎焊部件的孔隙率。为此，高速 X 射线辐射技术首次被用作高温钎焊应用中材料流现场分析的检查方法。现有的X射线辐射系统为此目的进行了调整，以满足高温钎焊的要求。这种新的检查方法能够通过非破坏性的原位观察方法来识别钎焊间隙中发生的与温度相关的运动过程，而不受光学检查过程的限制。高速 X 射线辐射还可以分析钎焊过程中不同时间润湿的边界层。对所识别的不同区域进行选择性金相分析并进行强度检查，从而将不同局部孔隙结构、反应层、结构和所得强度之间的关系与钎焊过程中的材料动力学相关联。除了对钎焊间隙中的材料运动进行现场检查外，高速 X 射线辐射还提供了以前所未有的质量分析润湿尝试的可能性。在视野内对开放润湿样品进行时间高分辨率观察，可以精确确定任何温度和停留时间下的润湿角。不会出现光学热台显微镜中已知的景深问题。对开放润湿尝试、不同宽度的钎焊间隙和不同温度下的传播速度进行综合检查，将确定润湿性、钎焊温度和间隙宽度对传播速度、孔径和孔密度的影响。这些认识使人们更好地了解 RAB 钎焊陶瓷复合材料中多孔缺陷的发展。通过对孔形成的原位观察，可以获得有关其行为随影响因素变化的基本知识。到目前为止，在技术上不可能在钎焊过程中进行现场分析。即使在其他钎焊工艺和材料组上转移所获得的知识也有助于提高 RAB 钎焊部件的密封性和使用寿命。