Bonding behavior studies of cold sprayed copper coating on the PVC polymer substrate

Metallization of the polymer surface by cold spray technique is an attractive way of improving their electrical conductivity and erosive resistance properties. However, it is still challenging to achieve a dense and thick high-strength metal coating, such as copper, on the polymer surface by cold spray system, due to excessive surface erosion during the processing. In order to overcome these difficulties, in the present work, two different types of interlayers are proposed. The polyvinyl chloride (PVC) polymer substrate was initially coated with a spherical copper powder and a tin powder separately and then a thick copper coating was fabricated using a dendritic copper powder. The properties of the coatings, such as shear adhesion strength, Vickers hardness and electrical resistivity, were measured and the influence of the interlayer on the above properties and bonding behavior was studied using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and focused ion beam dissection (FIB) techniques. The results show that the deposition efficiency is highly sensitive to the glass transition temperature of the substrate, irrespective of the process gas pressure. The coating with spherical copper interlayer shows poor shear adhesion strength due to the dislodged polymer debris at the spherical/dendritic copper coating interface. The electrical conductivity of the coating is fairly low as compared to the bulk copper due to the pores and inter-particle defects.