Friction and Wear of Flange and Shaft in Compressor under the Environments of PAG Oil and Carbon Dioxide as a Refrigerant

In order to protect the global environment, especially on the point of the greenhouse effect, carbon dioxide should be used as a natural refrigerant. Because new compressors with CO2 are going to be operated under the high pressure, the interaction between sliding surfaces in the compressor becomes very important. To develop new compressor, especially rotary type, the friction and wear characteristics of sliding surfaces were very important. In this paper, the surface interactions between a shaft and a flange, which were one of the contacting parts in compressor, were evaluated. The frictional forces and wear amounts in boundary lubricated sliding condition were measured using the pin-on-disk tester. Two types of refrigerants were used, namely R410A and CO2 to compare the tribological characteristics of conventionally used one with new natural refrigerant. It was found that CO2 lead to a bad lubricity as compared with R410A or pure oil due to the formation of relatively thin protective layer on the sliding surface. Smooth surface of shaft produced lower values of friction and wear than rough surfaces. The smooth surfaces represented much more spheroidal graphite, which had very favorable tribological characteristics, on the sliding surfaces.