High deposition efficiency and delamination issues during high-pressure cold spraying metallization of PEEK using spherical copper powders

Achieving high deposition efficiency (DE) is a current challenge of cold spraying metallization of polymers for developing surface function such as a conduction performance. Low-pressure cold spraying (LPCS) has been explored for that purpose but meets DE limitation less than 50% generally. This paper focuses on the possibility to overcome this issue, but using high-pressure cold spraying (HPCS). The anchoring of the copper powders onto the PEEK substrate is not difficult, but the deposition can fail during the coating build-up. A high pressure of 2.5 MPa without a gas preheating does not produce a coating build-up. Higher chamber pressures are required, but this implies to increase the gas temperature up to 400 degrees C to reach high deposition efficiency up to 70%. However, the absorption of the impact energy by the PEEK substrate during the collision of the powders generates an intermediate weakly bonded layer which is characterized by a decohesion between weakly deformed powders. This structure impairs the integrity of the coating during the additive deposition. Spalling damage occurs. Therefore, the deposition becomes very sensitive to delamination issues to overcome.