Polymeric Coatings With Superior Tribological Performance for Lightweight Materials in HFO-1234yf Refrigerant

Abstract

As global warming concerns continue to rise, research has shifted toward developing more climate-friendly refrigerants for air-conditioning and refrigeration compressors, with HFO-1234yf being a prominent candidate. In line with the need for lightweight engineering in electric vehicles, advanced composite coatings are necessary to improve the surface properties of parts and system components made from light metals such as magnesium and aluminum, which typically have poor tribological performance. This study investigates the tribological performance of advanced polymeric coatings (aromatic thermosetting copolyester [ATSP]-, polytetrafluoroethylene [PTFE]-, and polyether ether ketone [PEEK]-based) on lightweight aluminum alloy substrates in the presence of HFO-1234yf refrigerant and polyalkylene glycol (PAG) lubricant under starved lubrication conditions. Using a high-pressure tribometer, scuffing pressure, friction, and wear experiments were conducted, with all three coatings exhibiting excellent tribological performance compared to the bare substrate. Notably, PEEK and ATSP coatings demonstrated superior performance with high load-to-failure, low coefficient of friction, and negligible wear. Results also showed ATSP to have superior durability against a broad range of stress levels, while PEEK coating partially wears out at higher stress levels. These findings provide valuable insights for developing robust coatings on lightweight materials for high-stress applications.