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Development of a methodology for the quantitative prediction of the damage in to the diffusion layers of reactive air brazed BSCF-Steel-Joints

开发定量预测反应空气钎焊 BSCF 钢接头扩散层损伤的方法

基本信息

批准号：
392944287
负责人：
Dr. Markus Apel
金额：
--
依托单位：
Access e.V.
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 2021-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/392944287?language=en
关键词：
Development methodology quantitative prediction damage

项目摘要

Perovskite type ceramics like Ba0,5Sr0,5Co0,8Fe0,2O3-d (BSCF) are promising materials for the use as oxygen transport membranes (OTM) for oxygen separation from air. Supplying oxygen by membrane technology within a high temperature process can be more efficiently than other air separation techniques. For reliable working of the membranes at working temperatures of around 800°C, a gas tight joint between ceramic and metals is required. Reactive air brazing (RAB) was identified as a suitable technique for this material combination. Other brazing techniques are difficult to realize in the case of BSCF due to a thermodynamic instability of the material in vacuum. In the case of RAB, wetting of the silver copper braze occurs due to interface reactions between insito built CuO and BSCF. These reactions are required for wetting. The higher the CuO-content in the braze alloy is, the better the wetting is, although, at the same time a change of microstructure in the ceramic is visible, characterized by Cu-Co-Oxides at the grain triple points combined with micro cracks. Additionally, a reaction layer between steel and braze can be observed. Mechanical tests showed that both diffusion layers decrease the mechanical strength of the joints. The object is the development of a methodology for a quantitative prediction of damage inside of the diffusion layers of reactive air brazed ceramic steel joints.Hence, the first step should be a thermodynamic modelling of the system. Because an entire modelling of the overall system is not possible for ceramic / braze alloy / steel due to the complexity, the modelling is divided into four zones. With this data, structural analyses of the microstructure (grain structure, phase portion division and distribution) should be done in the reaction layer as well as in the braze - in its temporal development very near to reality. The calculated structures are a basis for the micromechanical simulation to predict the joint qualities and the damage development in the joints. Thereby, the infiltration of BSCF with the silver braze to generated variations of the qualities of the BSCF interface will be considered in particular. The interactions between the joining partners, the braze alloys of different composition and the different process parameters can be modelled by the simulation. The following micromechanical simulation is based on these simulated microstructures as well as on experimentally 2D and 3D structures (3D EBSD). The aim of the micromechanical simulation is the prediction of the damage development during brazing. Therefore, optimum brazing process parameters (Cu content, temperature, process) can be determined for the special case. The methodology should be transferable on other brazed joints. For example, similar reactions appear with other perovskite type ceramics (e.g., LSCF). With such a methodology, process parameters during brazing can be correlated directly with the mechanical qualities of the joints.

Ba 0，5Sr 0，5Co 0，8 Fe 0，2 O3-d（BSCF）是一种具有广阔应用前景的氧传输膜材料。在高温过程中通过膜技术供应氧气可以比其他空气分离技术更有效。为了使膜在约800°C的工作温度下可靠工作，陶瓷和金属之间需要气密接头。反应空气钎焊（RAB）被确定为一个合适的技术，这种材料的组合。在BSCF的情况下，由于材料在真空中的热力学不稳定性，难以实现其他钎焊技术。在RAB的情况下，润湿的银铜钎焊发生由于内部建立的CuO和BSCF之间的界面反应。这些反应是润湿所必需的。钎焊合金中的CuO含量越高，润湿性越好，尽管同时陶瓷中的微观结构的变化是可见的，其特征在于在晶粒三相点处的Cu-Co-氧化物与微裂纹结合。此外，可以观察到钢和钎焊之间的反应层。力学性能测试表明，两种扩散层均降低了接头的力学强度。目的是发展一种定量预测反应性空气钎焊陶瓷钢接头扩散层内部损伤的方法，因此，第一步应该是建立系统的热力学模型。由于陶瓷/钎焊合金/钢的复杂性，不可能对整个系统进行完整建模，因此将建模分为四个区域。利用这些数据，应在反应层以及钎焊中进行微观结构的结构分析（晶粒结构、相部分划分和分布）-其时间发展非常接近现实。计算得到的结构为微观力学模拟预测接头质量和接头损伤发展奠定了基础。因此，将特别考虑BSCF与银钎焊的渗透以产生BSCF界面质量的变化。通过模拟可以模拟连接伙伴、不同成分的钎焊合金和不同工艺参数之间的相互作用。下面的微机械模拟是基于这些模拟的微结构以及实验的2D和3D结构（3D EBSD）。微观力学模拟的目的是预测钎焊过程中的损伤发展。因此，最佳钎焊工艺参数（铜含量，温度，过程）可以确定的特殊情况。该方法应适用于其他钎焊接头。例如，类似的反应出现在其它钙钛矿型陶瓷（例如，LSCF）。通过这种方法，钎焊过程中的工艺参数可以直接与接头的机械质量相关。