SYMPOSIA PAPER Published: 01 January 2007
STP41654S

Characterization of Wear and Surface Reaction Layer Formation on Aerospace Bearing Steel M50 and a Nitrogen-Alloyed Stainless Steel

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The formation of reaction layers on surfaces in mechanical contact is strongly affected by the tribological loading conditions, the materials used, the lubricant and the service temperature. An appropriate balance between reactivity of material and lubricant in tribological systems decreases wear and friction and increases the durability. The goal of this paper is to compare the reaction layer formation on a standard aerospace bearing steel AMS 6491 (M50) with that on a high strength stainless steel grade AMS 5698 exhibiting a nominal chemical compositions of 0.82C-4.1Cr-1V-4.2Mo (wt. %) and 0.3C-0.4N–15.2Cr-1Mo (wt. %), respectively. As lubricant jet engine oil Mobil Jet II has been used. Rolling contact fatigue (contact pressure: 6 GPa) and ball-on-disk tests (contact pressure: 1.6 GPa, sliding speed 10 cm/s) at room temperature and at 150°C were employed to study the effect of extreme loading conditions and temperature dependence of the reaction layer formation. The contact areas were inspected by means of optical profilometry, scanning electron microscopy (SEM), and secondary ion mass spectrometry (SIMS) in order to determine type, thickness, homogeneity, and distribution of the reaction layers in the contact zone. The main result of the study is that the reaction layer formation is significantly less on the stainless steel grade compared with M50. SIMS depth profiles were determined in order to explain the differences in the wear characteristics of the two materials. The reaction layers are mainly built up of PXOY molecules, which might be phosphates resulting from the tricresyl phosphate (TCP) lubricant additive. The role of the chemical reaction of the steel and TCP regarding the layer formation will be discussed.

Author Information

Peissl, Sven
Materials Center, Leoben, Austria
Leitner, Harald
University of Leoben, Austria
Ebner, Reinhold
Materials Center, Leoben, Austria
Hutter, Herbert
Institute for Chemical Technologies and Analytics, Vienna University of Technologies, Vienna, Austria
Krecar, Dragan
Institute for Chemical Technologies and Analytics, Vienna University of Technologies, Vienna, Austria
Rabitsch, Roland
Boehler Edelstahl GmbH, Kapfenberg, Austria
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Developed by Committee: A01
Pages: 214–223
DOI: 10.1520/STP41654S
ISBN-EB: 978-0-8031-6209-9
ISBN-13: 978-0-8031-3491-1