Modeling the interaction between surface condition and diffusion characteristics for diffusion bonding of nickel alloys

在整个表面上连接有或没有层间材料的异种焊缝和相似焊缝是扩散连接的特征。这使得扩散键合特别适用于制造单片元件，例如在由大量层或片组成的微型仪器工程中。在这种微型设备中，冷却、化学混合或化学反应等过程可以以比传统系统更高的效率进行。根据与工艺相关的操作条件，这些部件使用高性能材料，如镍合金。提高微仪器效率的另一种可能性是增加每组分体积的反应面积。这就要求大幅度减小通道结构的尺寸，因此必须降低扩散键合过程中的工艺能量（连接温度、连接时间和连接压力），以保证通道结构的尺寸精度以及所需的材料和连接性能。在本项目中，将研究如何通过车削和金刚石平滑工艺来塑造连接表面的微观结构和表面性能，以增加扩散系数，从而降低工艺能量。科学目标是确定导致镍和625合金在车削和金刚石平滑过程中表面粗糙度、晶粒尺寸和残余应力状态变化的机制和相互关系。此外，对这些材料的几何表面和物理表面层性能之间的关系，扩散键合的工艺制度，以及由此产生的接头的性能进行了确定。此外，根据调查结果，接触角测量应以这样一种方式进行认证，以便对连接表面进行快速简便的评估，以便能够预测所需的过程能量。由此，建立了一个模型，该模型基于连接面接触角和表面粗糙度的输入变量，能够推导出适合扩散连接的工艺条件。

Dissimilar and similar welds joined over the entire surface with or without interlayer materials are characteristics of diffusion bonding. This makes diffusion bonding particularly suitable for manufacturing of monolithic components, e.g. in microapparatus engineering, which are composed of a large number of layers or sheets. In such microapparatuses, processes such as cooling, chemical mixing or chemical reactions can be carried out at higher efficiencies than in conventional systems. Depending on the process-related operating conditions, high-performance materials such as nickel alloys are used for these components. An additional possibility to improve the efficiency of microapparatuses is to increase the reaction area per component volume. This requires a significant reduction in the size of the channel structures, so that the process energies during diffusion bonding (joining temperature, joining time and joining pressure) must be reduced in order to ensure the dimensional accuracy of the channel structures and the required material and joining properties. In this project, research is to be carried out into how the microstructure and surface properties of the joining surfaces must be shaped by turning and diamond smoothing processes in order to increase the diffusivity and thus reduce the process energies. The scientific objectives are to determine the mechanisms and interrelationships that lead to a change in the surface roughness, grain size and residual stress state during turning and diamond smoothing of nickel and Alloy 625. Furthermore, for these materials the determination of the relationships between the geometrical surface and the physical surface layer properties, the process regime of diffusion bonding, and the properties of the resulting joint is carried out. In addition, based on the results of the investigations, the contact angle measurement is to be qualified in such a way that a quick and easy evaluation of the joining surfaces can be made in order to enable a prediction of the required process energies. From this, a model is to be developed which, on the basis of the input variables contact angle and surface roughness of the joining surfaces, enables the derivation of suitable process conditions for diffusion bonding.