Improving deposition efficiency and inter-particle bonding of cold sprayed Cu through removing the surficial oxide scale of the feedstock powder

Abstract

In cold spray, surficial oxide scale of the feedstock powder not only reduces the deposition efficiency of spraying powder, but also deteriorates the properties of the deposit due to its influence on inter-particle bonding. To simultaneously improve the deposition efficiency of spraying powder and the properties of the deposit, in this study, taking Cu as a typical material, acid pickling was used to remove the oxide scale on the surface of the as-received powder. During acid pickling, Cu powder particles were immersed into the acid alcohol solution and then dried in a low-pressure tank. Using the as-received powder and acid-pickled powder as the spraying powder, Cu deposits were prepared under the same spraying conditions. The deposition behavior of spraying powders, the microstructure and properties, including mechanical properties, conductivities and anti-corrosion behavior of the Cu deposits were systematically studied. Results show that acid pickling can effectively remove the oxide scale on the surface of the as-received powder and reduce the powder oxygen content from 0.12 wt% to 0.044 wt%, leading to an increase in deposition efficiency of the spraying powder from 74% to 84%. Although both the Cu deposits reveal dense microstructure and thereby show good anti-corrosion, the tensile properties and conductivities of Cu deposits, which are sensitive to the inter-particle bonding, decrease with increase of the oxygen content in spray powder. Cu deposit prepared by acid-pickled powder shows the superior tensile properties and conductivities, and the tests yielded the tensile strength of 245 MPa, Young modulus of 85 GPa, electrical and thermal conductivities of 90%IACS and 298 W·m−1·K−1. Therefore, it is an effective approach to improve the deposition efficiency of spraying powder and prepare high-property cold-sprayed metallic deposit simultaneously by using acid pickling to remove the surficial oxide scale of particle.