A study on the powder manufacturing effect on flowability and deformability of pure Cu powders in cold spray application

Feedstock powder plays an important role in the properties of cold spray deposition. However, tailoring powders specifically for cold spray application has been a challenge as most commercially available powders are not designed and/or optimized for cold spray process. In this research, microstructural and mechanical properties were evaluated to identify various powder characteristics for yielding the optimized coating properties. Deformability and flowability of different Cu powders produced by gas atomization and electrolysis processes were investigated and compared. The spherical morphology of gas-atomized powders provides less surface area when compared with irregular-shaped electrolytic ones. Low surface area contributes to smooth powder flow, prevents their extensive oxidation to atmospheric condition and facilitates the development of dense coatings, as revealed by their microstructural features. The relationship between feedstock characteristics and cold sprayed coatings were studied in terms of porosity, flattening ratio and microhardness. Satellite-free gas-atomized powder resulted in a better deposition quality (porosity ≈ 0.66 %, flattening ratio ≈ 3.57 and microhardness ≈ 107 HV) under low-pressure cold spray (LPCS) system. This may be attributed to thinner oxide layer, and exhibiting highly deformed particles during deposition. Thus, satellite-free gas-atomized powder may hold promise as an optimized feedstock for Cu LPCS deposition.