Abstract
The aim of this study was to investigate the microstructure (including surface roughness, microstructure and microhardness) of cold sprayed copper coatings on 2017 Al alloy, before and after annealing at 350°C for 1h. It seemed that keeping constant the powder flow rate and increasing the gas pressure from 2.0 to 2.5 MPa, the surface roughness of the coating tended to decrease, while the thickness of the coating tended to increase. Also, it seemed that keeping constant the pressure and increasing the powder flow rate from 22 to 130 g/min, the surface roughness and the thickness of the coating tended to increase. The microstructural study of the coatings after etching revealed particle interfaces and in some cases grain boundaries. Twins were observed in some of the coatings. Negligible porosity, absence of cracks and good adhesion of the coatings to the substrate were observed. The microhardness of the coatings varied between 95 HV0.3 and 150 HV0.3 for the different employed cold sprayed conditions. After coatings’ annealing the microhardness of all the coatings (cold sprayed and HVOF sprayed) decreased. The aforementioned results were compared with those of HVOF coating.
