The carbon dioxide (CO2) is investigated as an alternative refrigerant to replace HFC
(hydro fluorocarbon) refrigerants in refrigerators and air conditioning systems due to the
environmental concerns. Because new compressors with the carbon dioxide are going to be
operated under the high pressure, the tribology of sliding surfaces in the compressor becomes very
important. To develop new compressors, especially rotary type, the friction and wear characteristics
of sliding surfaces between a vane and a roller in the rotary compressor were evaluated in this
paper. Several hard coatings, such as TiN, CrN, and WC/C, were applied on vane surfaces in order
to improve the tribological characteristics, and their performances were evaluated experimentally.
The vane-on-disk type sliding tests were carried out under the various sliding speeds, normal loads,
and carbon dioxide pressures with an exclusive high pressure wear tester. From the tests wear
volume of vane surfaces applied various coatings were compared. During the tests coefficients of
friction and surface temperatures were monitored. Test results showed that WC/C coatings showed
good tribological properties. TiN and CrN coated vanes showed good wear resistance properties but
produced high friction.