Wear Mechanisms of Gray Cast Iron in the Presence of Environmentally Friendly Hydrofluoroolefin Based Refrigerant and the Effect of Tribofilm Formation

Abstract

Hydrofluoroolefinbased refrigerant (2,3,3,3tetrafluoropropene, namely, HFO1234yf), which has been developed as an environmentally friendly refrigerant, is proposed as a direct replacement solution in automotive airconditioning compressor applications. In the present work, the wear mechanisms of this refrigerant using gray cast iron interfaces were investigated under a wide range of operating conditions. A critical velocity was measured from scuffing type experiments, where beyond that maximum interfacial loads did not change significantly with sliding velocity, suggesting a mechanical rubbingtype wear mechanism. Below the critical velocity, scuffing loads decreased almost linearly with sliding velocities. Wear type experiments identified two different wear mechanisms, namely, oxygendominating and fluorinedominating wear, depending on sliding velocities and normal loads. Oxygendominating wear mechanism prevailed under low sliding velocities and normal loads. In contrast, fluorinedominating wear was predominant under moderate sliding velocities and low or moderate loads. The formation of protective tribofilms and their effect on the wear mechanism was used to construct a wear map.