Tribological performance comparing different refrigerant-lubricant systems: The case of environmentally friendly HFO-1234yf refrigerant

We report on the tribological performance of gray cast iron with different lubricants, namely PAG (Polyalkylene glycol), POE (Polyolester), and Mineral oil, in the presence of environmentally friendly HFO-1234yf refrigerant. Two operating temperatures (24 °C and 110 °C) were used to investigate the mutual solubility of lubricant/refrigerant systems. PAG/HFO-1234yf exhibited better tribological performance compared to the other systems. The better performance was attributed to lower solubility of PAG in HFO-1234yf refrigerant, thus allowing the lubricant and refrigerant to preserve their unique properties. Using Scanning Electron Microscopy, plastic flow associated with adhesive wear was revealed for PAG/HFO-1234yf, where an anti-wear film over the surface was also identified. X-ray Photoelectron Spectroscopy identified a fluorine enriched protective layer in the case of PAG/HFO-1234yf at 110 °C.