Friction and Wear Characteristics of Lubricants for Alternative Refrigerant HFC 134a

Abstract

The friction and wear characteristics in an althernative refrigerant HFC 134a were investigated using a ball-on-plate type apparatus.The lubricants used were polyalkylene glycol(PAG)and polyol ester(POE), which have high mutual solubility with HFC 134a.The results obtained are as follows.(1)With PAG, the HFC 134a formed fluoride on the rubbing surfaces, which improved the friction and wear characteristics.In contrast, POE with high adsorption ability showed poor friction and wear performance above the transition temperature of about 150°C to prevent the formation of fluoride, although it exhibited exhibited excellent friction and wear performance below the transition temperature.(2)The addition of TCP of aryl-type phosphate ester to PAG improved the friction and wear characteristics owing to the absorption film of TCP in a low temperature range and the formation of iron phosphate in a high temperature range.(3)With POE containing MoDTC the coefficient of friction as low as 0.05 was attainable owing to the formation of MoS₂ in HFC 134a at temperatures below the transition temperature although HFC 134a did not contain oxygen.