Investigation on the microstructure, phase formation and properties of aluminium alloy coatings by stud spraying

This study aims to investigate a novel spraying technology. The spraying technology is named stud spraying since it has been developed by improving the traditional stud-welding process. Al–Cu coatings have been prepared on the surface of copper plates by using aluminium studs with bosses, and the thickness of the coating centre can be 15–30 μm under the height of stud boss (0.2 mm). The microstructure, phase structure and composition of the coating are characterized. The results show that a large number of Al–Cu intermetallic compounds and a few oxides are present in the coating. Numerous growth crystals are present at the metal interface between the coatings and the copper plate. The crystal morphology of the interface metal is growing from the copper plate to the coating metal which has also been enhanced the coating interface. The stud-coating process is a rapidly cooling solidification process that a variety of intermetallic compounds including θ phase (Al 2 Cu), η 2 phase (Al 48 Cu 52 ), ζ 2 phase (Al 9 Cu 11 ) and γ 2 phase (Al 4 Cu 9 ) are present within the layers. In addition, multiphase intermetallic compounds enhanced the surface microhardness of the coating with its value increasing from 85 to 222 HV.