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ACRC Technical Report 211PDF


Title:Fundamental Investigation on the Tribological Failure Mechanisms of Compressor Surfaces, Scuffing: Detailed Roughness Analysis of Al390-T6
Author(s):Suh, A.Y.; Polycarpou, Andreas A.; Conry, T.F.
compressor surfaces
tribological failure mechanisms
Abstract:Scuffing that occurs at tribological contacts in mechanical components, brings about topographical, chemical, and mechanical changes mainly at the sub-micron surface. In this project, extensive studies involving the use of various engineering and scientific tools were performed to better understand the exact mechanisms behind this phenomenon. A High Pressure Tribometer (HPT) was used to simulate shoe-on-disk tribological contacts under various conditions as encountered in compressor surfaces. Specifically, Al390-T6 disk/52100 steel pin tribo-pairs are representative of typical contacting surfaces used in swash plate-type air-conditioning compressors. Once the time to scuff a sample under the test protocol was determined, subsequent HPT tests were stopped at 0.25 x Scuffing Time, 0.50 x Scuffing Time, and 0.75 x Scuffing Time intervals. The progressive change in disk topography leading up to scuffing was first observed in the 1-D roughness study [1], but more extensively captured by the 2-D Birmingham-14 roughness characterization that is also described in this report [2]. When the chemical analyses were conducted on the uppermost surfaces for depths of 120 nm, significant changes in some of the major chemical element concentration were revealed at scuffing. The major chemical compositional changes include a depletion of silicon, which was used to strengthen the aluminum alloy, and a drastic increase of oxygen component, signaling heavy oxidation at scuffing [1]. The mechanical properties of the disks undergoing tribological evolution were also investigated through various experimental hardness measurements, ranging from macro- to micro-, and to nanoscales [3]. Based on the experimental hardness results, it was found that the hardness of the material becomes higher at the micro- and sub-micro scales than the bulk, regardless of the amount of wear towards scuffing. It was also observed that there was a gradual weakening of the uppermost 60 nm. In this report, we describe in detail the surface roughness changes that occur to the Al390-T6 samples as they undergo progressively longer tribological testing, eventually leading to scuffing. [1] Patel, J.J., Polycarpou, A.A., and Conry, T.F., 2002, “Investigation of the Scuffing Mechanism Under Starved Lubrication Conditions Using Macro, Meso, Micro, and Nano Analytical Techniques,” ACRC TR-191, University of Illinois. [2] Suh, A.Y., Polycarpou, A.A., Conry, T.F., 2003, “Detailed Surface Roughness Characterization of Engineering Surfaces Undergoing Tribological Testing Leading to Scuffing,” Wear, in press. [3] Pergande, S.R., Polycarpou, A.A., and Conry, T.F., 2002, “Use of Nano-Indentation and Nano-Scratch Techniques to Investigation Near Surface Material Properties Associated with Scuffing of Engineering Surface,” ACRC TR-193, University of Illinois.
Issue Date:2003-03
Publisher:Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report:Air Conditioning and Refrigeration Center TR-211
Genre:Technical Report
Sponsor:Air Conditioning and Refrigeration Project 127
Date Available in IDEALS:2009-06-12

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