Cold spray coating of PEEK surface by copper deposition: Interfacial adhesion at high deposition efficiency and bonding strength

Copper metallization of PEEK were performed by high-pressure cold spraying (HPCS) to obtain a high deposition efficiency (DE). Cu/PEEK interface and Cu/Cu interface produced under the same HPCS deposition conditions were compared in terms of feature and bonding strength. The DE of the Cu/Cu combination is 73% whereas the Cu/PEEK case gives a DE of 79%. These DE values are comparable whereas the bonding strengths are very different. The Cu/Cu interface reached values of 30-50 MPa while the Cu/PEEK interface was less resistant (0.2-10 MPa). SEM observations of the fracture surfaces exhibit the differences between these two combinations. The particles were less deformed and showed apparent decohesion for the Cu/PEEK case. In addition, craters due to particles decohesion and rebound were observed whereas the Cu/Cu case showed more particle flattening. The Cu/PEEK debonding was characterized by an adhesive failure. The copper powders that penetrated the PEEK substrate came out leaving craters. In addition, the weakly bonded Cu/Cu particles within the Cu/PEEK interface were conducive to a rupture. These features explain the low bonding strength of the Cu/PEEK interface. In case of Cu/Cu combination, the interface breaks by cohesive failure and the fracture surface evidenced flattened particles within the deposit. The greater adhesion strength of the Cu/Cu interface is then due to a more plastic deformation produced during the inter-collision of Cu powders during the HPCS deposition. (c) 2021 CIRP.