The authors tested the effects on the tribological characteristics of refrigeration oils under refrigerant atmospheres using a block-on-ring tribometer. Based on the results of a sliding test using the tribometer, it was found that tricresyl phosphate (TCP) in both a polyol ester (POE) and alkylbenzene (AB) oil formed a lubricating film on the sliding surface under R410A atmosphere. Surface analyses revealed that a phosphate film had been formed on the sliding surface. With the POE oil in particular, the anti-wear effect of TCP greatly reduced the width of the wear track. It was also found that R32 interferes with the formation of phosphate films to a greater extent than does R410A. It is thought that the high polarity and the high reactivity of R32 with nascent metal surfaces prevent TCP from adsorbing to the Fe of the sliding surface. These results show that not only refrigeration oils but also refrigerants can have a major effect on the formation of the phosphate film in refrigeration systems. This knowledge could be helpful when designing new refrigeration systems.

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