Discharge Characteristics and Dynamic Process of Directional Spraying Binary and Ternary Alloy Coating via Electrical Explosion Method

Electrical explosion spraying, due to its high reaction temperature and intense mechanical effect, like strong shock wave and high-speed expanded explosive products, is a kind of satisfactory thermal spraying method. It had used to prepare single- or multi-element wire coating; however, the investigation of middle physical process was lacked, which was not beneficial to deeply understand the coating formation characteristics with the explosive process. In this study, a directional electrical explosion device was designed, which was available for synthesizing dense and homogeneous coating. Experiments were performed with intertwined Cu-Ni wire, and intertwined Cu-Ni-Al wire. Electrical and radiational diagnoses including current/voltage waveforms and self-emission images were used to investigate the explosive characteristics. SEM and XRD characterizations were used to study the morphology and crystallography of the produced coating. For intertwined two-wire (Cu-Ni) explosion, the parameters were measured separately to explore more details according to the corresponding dynamic high-speed images. The results indicated that the multi-wire explosion was non-synchronously with different explosive behaviors of wires; therefore, the discharge product channel showed a mixture of plasma, un-ionized metal vapor, and un-vaporized metal drops. Accordingly, the sprayed coating was composed by μm-scaled chunks or plates with some nanoparticles adhering on them.