Tribological Behaviors of 52100 Steel in Carbon Dioxide Atmosphere

Abstract

The tribological behavior of 52100 steel in a carbon dioxide (CO 2 ) atmosphere was investigated using a reciprocating ballon-disk tribometer. X-ray photoelectron spectroscopy (XPS) was used to identify the adsorbed surface layers and tribochemical products. We found that CO 2 can substantially reduce friction and wear of the steel. Adsorbed and reacted surface layers containing iron carbonate and/or bicarbonate play an important role in reducing friction. A disk, exposed once to CO 2 atmosphere, also shows a low friction for a long time even in a vacuum environment. An optimum CO 2 pressure exists for effectively reducing friction and wear. A low-pressure CO 2 atmosphere is insufficient to produce iron carbonate. In contrast, high pressure engenders serious chemical wear.

Tribological investigation of cast iron air-conditioning compressor surfaces in CO2 refrigerant

“…Furthermore, due to contamination, the evidence of the carbonate formation is not very clear and may be hindered by other compound formations however it has been shown by other researchers that CO 2 promotes carbonate formation. The XPS results indicate the existence of iron carbonates due to the presence of CO 2 refrigerant, which is in agreement with findings by Wu et al [8], where they showed that formation of carbonates is possible in 52100 Steel. In their study, different pressures of CO 2 were investigated and it was noted that the higher the pressure of CO 2 , the more the iron carbonate formation.…”

“…This surface ''polishing'' effect was generated by mild wear process or burnishing. Based on the optical micrographs depicted in figure 3 and the friction coefficient values for the different cases, it could be ascertained that adhesion is the main wear mechanism in the cases of N 2 , air and R134a environments, while for the O 2 environment the main wear mechanism was oxidation and for the mild burnishing in the case of CO 2 is chemical wear, in agreement with [8]. Based on these results, the wear mechanism in the cases of O 2 and CO 2 environments is different because CO 2 is fully oxidized as it is a common byproduct compound of the oxidation process whereas O 2 , due to its electronegativity forms chemical bonds with most metals.…”

“…However, the pressures they studied were much lower than the pressures studied in this work. Specifically, the reported findings in [8] are for pressures up to atmospheric pressures (0.10 MPa), which are unrealistically low for CO 2 operating compressors. In the present work we have specifically investigated realistic compressor operating conditions with a tribotester that was specifically designed and manufactured to allow for very high pressures (up to 13.8 MPa).…”

“…In their study, different pressures of CO 2 were investigated and it was noted that the higher the pressure of CO 2 , the more the iron carbonate formation. It should be also noted that in [8] it was found that higher pressure of CO 2 produces chemical wear and that an optimal operating range of pressures may exist. However, the pressures they studied were much lower than the pressures studied in this work.…”

“…The environmental advantages of CO 2 have been widely reported in recent years [4], where it was shown that CO 2 is thermodynamically capable, efficient and comparable to state-of-the-art HFC refrigerants currently used. However, its tribological performance and effects on wear and scuffing are not well understood and remain a subject of study by different researchers [5][6][7][8]. When CO 2 was first introduced it was believed that the oxygen present in the CO 2 molecule might have a beneficial role to the tribological performance of material interfaces as it could promote protective oxide formations.…”