Tribological performance of environmentally friendly refrigerant HFO-1234 yf under starved lubricated conditions

Concerted research efforts have been made in the field of alternative refrigerants due to environmental concerns. Newly developed, HFO-1234 yf (2,3,3,3-Tetrafluoropropene) refrigerant has been proposed as a direct replacement solution for substituting the existing harmful hydrofluocarbon refrigerants, such as R134a (1,1,1,2-Tetrafluoroethane). This paper presents a comparative tribological study of R134a and HFO-1234 yf refrigerants. Specifically, we present scuffing resistance, friction and wear, using gray cast iron interface under starved lubricated conditions. Better tribological performance was observed with HFO-1234 yf, compared to R134a. Optical microscopy and profilometry techniques were employed to analyze wear, and scanning electron microscopy was carried out to reveal the morphological changes along with the mode of wear. Chemical composition of the substrate was studied using energy dispersive X-ray spectroscopy, which showed the presence of fluorine element in the case of HFO-1234 yf refrigerant. This result in conjunction with the X-ray photoelectron spectroscopy results (disks and pins analyses), support the presence of fluorine-containing tribolayers preventing metal-metal contact and sustaining prolonged interface functionality.