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

该项目的目的仍然是澄清陶瓷基体上使用铝涂层的冷气动力喷涂金属涂层的附着机理。这一目标得到了冷气动态喷涂金属/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制的分析，扩展了项目前期提出的关于陶瓷基片与金属涂层界面结合机理的基本模型，使原来关注的单晶和多晶Al_2O_3基片得到了Si_3N_4、SiC、MgF_2和AlN的补充。这一选择涵盖了技术相关性和有关化学键合条件（涉及离子键合份额）的显著差异。计划的调查现在集中在这些不同的粘结条件对涂层附着力的相应机制的影响。为了完成参数矩阵，涂层过程中的基体温度，原料粉末分数和随后的热处理也是变化的，并评估它们对涂层/基体界面形成和涂层结合强度的影响。用REM、TEM、XRD、EELS等方法分析和描述了金属/陶瓷界面的结合状况。开发精确的涂层附着力模型的一个重要工具是对相同基底陶瓷上的铝PVD涂层进行类似的研究。典型的逐原子PVD涂层形成允许形成金属/陶瓷界面，而没有宏观和介观类型的缺陷，如喷涂过程中出现的缺陷。因此，PVD涂层的研究允许描述由衬底和涂层材料之间的晶格失配引起的界面缺陷。所获得的结果都增加了新的见解，陶瓷上的金属的PVD涂层的形成，并有助于正确地解释从CGS接口调查的结果。

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.