Beneficial role of the continuous powder oxide film in establishing chemical bonding at cold sprayed Al coating/PEEK substrate interface

Cold spray has emerged as a viable technique for polymer surface metallization, featuring a low process temperature and high deposition rate. In literature, it is generally believed that the formation of metallurgical/ chemical bonding is impossible to realize during cold spray metallization of thermoplastics. However, there is no clear evidence to support this argument, hence the exact nature of bonding mechanism is still unclear and debatable. In this study, for the first time, the adhesive feature of cold sprayed Al coating on polyetheretherketone (PEEK) substrate was studied in detail by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), confirming the presence of chemical bonding at the Al/PEEK interface. The TEM images showed that the combination of Al coating and PEEK substrate is strongly related to the presence of continuous oxide film at the interface. Moreover, the FTIR and XPS results revealed that the metal-polymer complex was formed at the PEEK/amorphous oxide interface, which resulted in chemical bonding at Al/PEEK interface.