Contribution to clarify the adhesion mechanisms of cold gas dynamic sprayed coatings

拟议项目的目的仍然是澄清冷气动力喷涂金属涂层在陶瓷基材上使用铝涂层的结合机理。这一目标得到了冷气动力喷涂金属/陶瓷层压板和复合材料日益重要的支持，例如在能源和汽车应用中。通过对陶瓷基片与金属涂层界面的化学物理机理的分析，扩展了一期工程所建立的陶瓷基片与金属涂层间结合机理的基本模型，从而用氮化硅、氮化硅、氟化镁和氮化铝等材料补充了原有的单晶和多晶氧化铝基片。这一选择既包括技术上的相关性，也包括与离子键份额有关的化学键条件的显著差异。计划中的调查现在集中在这些不同的结合条件对涂层附着力的后续机制的影响上。为了完善参数矩阵，还改变了涂层过程中的基材温度、原料粉料含量和后续热处理，并评价了它们对涂层/基材界面形成和涂层结合强度的影响。用X射线衍射仪、透射电子显微镜、X射线衍射仪和电子能谱等分析和描述了金属/陶瓷界面的结合和结合情况。建立准确的涂层附着力模型的一个重要工具是对同一衬底陶瓷上的铝PVD涂层进行相似研究。典型的逐个原子的PVD涂层形成允许形成金属/陶瓷界面，而没有宏观和细观类型的缺陷，如喷涂过程中出现的缺陷。因此，对PVD涂层的研究可以描述由于基片和涂层材料之间的晶格失配而导致的界面缺陷。所获得的结果为金属在陶瓷表面的PVD涂层的形成提供了新的见解，并有助于正确解释CGS界面调查的结果。

The aim of the proposed project prosecution still is the clarification of the adhesion mecha-nisms of cold gas dynamic sprayed metallic coatings using aluminium coatings on ceramic substrates. This aim is backed by the increasing significance of cold gas dynamic sprayed metal/ceramic laminates and composites e.g. in energy and automotive applications. By ana-lysing the chemico-physical mechanisms on the interface between ceramic substrate and metallic coating, the basic model on adhesion mechanisms which results from the first project period will be extended.Hence, the formerly focused single- and polycrystalline Al2O3 substrates are complemented by Si3N4, SiC, MgF2 and AlN. This selection covers both technological relevance and signifi-cant differences concerning the chemical bonding conditions referred to the share of ionic bonding. The planned investigations now focus on the resulting influences of these different bonding conditions on the consequential mechanisms of the coating adhesion. To complete the parameter matrix, substrate temperature during coating, feedstock powder fraction and subsequent heat treatments are also varied, and their influence on the coating/substrate in-terface formation and the coating adhesion strength are evaluated. The adhesion and bonding conditions within the metal/ceramic interface are analysed and described using the methods of REM and TEM as well as XRD and EELS. An important tool to develop the exact coating adhesion model is the similar investigation of aluminium PVD coatings on the same substrate ceramics. The typical atom-by-atom PVD coating formation allows the formation of metal/ceramic interfaces without macro- and meso-type defects, like those that occur from spraying processes. Hence, the investigations of PVD coatings allow the description of interface defects resulting from lattice misfits between the substrate and the coating material. The gained results both add new insights to the PVD coating formation of metals on ceramics and help to correctly interpret findings from the CGS interface investigations.