Aerosol deposition of alumina ceramic coatings on polyether ether ketone (PEEK) for high-voltage insulation

In future electric propulsion systems, electrical devices are required to operate in more severe environments, such those involving high voltages and temperatures, in order to meet the increased power demand. The commonly-used polymeric insulation systems for metallic conductors may be subjected to thermo-chemical degradation induced by localised partial discharge phenomena, which may occur at the surface or within the bulk of the material. In the present work, particulate aerosol deposition (AD) was employed as a dry and high-speed spray coating method to fabricate dense ceramic coatings at room temperature onto polyether ether ketone (PEEK) substrates. High voltage electrical endurance tests were conducted using a 1 kVrms, 1 kHz voltage source until sample breakdown occurred after successive partial discharges. The PEEK substrates coated with a protective alumina film (∼4.3 μm thick) showed significantly enhanced electrical durability, surviving approximately 60 times longer than the uncoated reference material in an accelerated lifetime test. These results demonstrate the excellent potential of protective ceramic coatings produced by AD to mitigate the effects of partial discharge in polymeric electrical insulation systems.