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Significance statement
This paper includes original work dealing with the tribological behavior of Al-390T6, Mn-Si Brass, and Gray cast iron as common interfaces for air-conditioning and refrigeration compressors in the presence of carbon dioxide (CO2). Experimental testing was carried out through a specialized tribometer using a pin-on-disk configuration against 52100 steel shoes.
Wear experiments (constant normal load) show overall better performance in terms of wear of gray cast iron compared to Al-390T6 and Mn-Si Brass. Even though Al-390T6 and Mn-Si Brass have similar hardness, profilometric measurements show more wear in the case of Al-390T6 compared to Mn-Si Brass. Using XRF and AES it was shown that silicon particles are being pulled out throughout the testing of Al-390T6 losing strength during sliding.
Journal Reference
Wear, Volumes 326–327, 2015, Pages 28–35. Emerson Escobar Nunez1, Andreas A. Polycarpou2.
- Grupo de Investigación en Tecnologías para la Manufactura (GITEM), Departamento de Energética y Mecánica, Universidad Autónoma de Occidente, km 2 Vía Cali-Jamundí, Cali-Valle, Colombia.
- Department of Mechanical Engineering, University of Texas A&M, 3123 TAMU, College Station, TX 77840, USA.
Abstract
The implementation of carbon dioxide (CO2) as an alternative refrigerant for air-conditioning compressors has gained significant attention recently. The main interest in CO2 is related to its zero ozone depletion potential (ODP) and low global warming potential (GWP) compared to commonly used hydroflurocarbon (HFCs) refrigerants such as R-134a. Friction and wear studies on tribological contacts commonly used in air-conditioning compressors under the presence of CO2 are scarce in the literature. The present study focuses on the tribological behavior of Al390-T6, gray cast iron, and Mn–Si–brass (UNS C67300). These materials were tested against 52100 steel shoes using a pin-on-disk configuration. The tests were performed under submerged lubrication conditions using polyalkylene glycol (PAG) lubricant in the presence of CO2. Results showed that the wear resistance of gray cast iron and Mn–Si–brass was higher compared to Al390-T6. In spite of the fact that Al390-T6 and Mn–Si–brass had similar hardness, Al390-T6 showed higher wear after testing. X-Ray Fluorescence (XRF) analysis of the lubricant after testing of Al390-T6 showed the presence of eutectic silicon particles. Also, Auger Electron Spectroscopy (AES) of Al390-T6 showed an atomic concentration decreased in silicon content after testing. Decreased in silicon content was attributed to the depletion of eutectic silicon particles, leading to a decrease in hardness and a subsequent increase in wear during the test.
