Application of soft X-ray absorption spectroscopy in chemical characterization of antiwear films generated by ZDDP Part I: the effects of physical parameters

Application of soft X-ray absorption spectroscopy in chemical characterization of antiwear films... X-ray absorption near edge structure (XANES) spectroscopy has been used to study the chemical nature of the antiwear films generated on steel surfaces using zinc dialkyldithiophosphates (ZDDPs). The spectra were recorded using total electron yield (TEY) and fluorescence yield (FY) to investigate the chemical nature of P, S, Ca, O and Fe on the surface and in the bulk, respectively. In the first part of this study, the effects of physical parameters on the composition and mechanism of antiwear film formation is discussed. It has been found that lower concentration of ZDDP, higher temperature and higher load all increase the rate of ZDDP decomposition; and longer rubbing time, higher concentration of ZDDP, moderate temperature, higher load and smooth surfaces help to form long chain polyphosphates. The sulphur in the film in most of the cases is in the reduced form. The presence of sulphate in very short rubbing times or high temperatures has also been detected. When the spectra from the TEY mode and FY mode were compared, a layered structure was found in most of the films. In these films, there is a longer chain polyphosphate on the topmost surface and a shorter chain polyphosphate in the bulk. At short rubbing times and low temperature, unchanged ZDDP is also present in the film. Depth profiling using X-ray photoelectron spectroscopy showed that the antiwear film formed in 30 min is thinner compared with a 12 hour film. Based on the above information, a new mechanism for antiwear film formation is proposed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Wear Elsevier

Application of soft X-ray absorption spectroscopy in chemical characterization of antiwear films generated by ZDDP Part I: the effects of physical parameters

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Publisher
Elsevier
Copyright
Copyright © 1997 Elsevier Ltd
ISSN
0043-1648
eISSN
1873-2577
D.O.I.
10.1016/S0043-1648(96)07272-9
Publisher site
See Article on Publisher Site

Abstract

X-ray absorption near edge structure (XANES) spectroscopy has been used to study the chemical nature of the antiwear films generated on steel surfaces using zinc dialkyldithiophosphates (ZDDPs). The spectra were recorded using total electron yield (TEY) and fluorescence yield (FY) to investigate the chemical nature of P, S, Ca, O and Fe on the surface and in the bulk, respectively. In the first part of this study, the effects of physical parameters on the composition and mechanism of antiwear film formation is discussed. It has been found that lower concentration of ZDDP, higher temperature and higher load all increase the rate of ZDDP decomposition; and longer rubbing time, higher concentration of ZDDP, moderate temperature, higher load and smooth surfaces help to form long chain polyphosphates. The sulphur in the film in most of the cases is in the reduced form. The presence of sulphate in very short rubbing times or high temperatures has also been detected. When the spectra from the TEY mode and FY mode were compared, a layered structure was found in most of the films. In these films, there is a longer chain polyphosphate on the topmost surface and a shorter chain polyphosphate in the bulk. At short rubbing times and low temperature, unchanged ZDDP is also present in the film. Depth profiling using X-ray photoelectron spectroscopy showed that the antiwear film formed in 30 min is thinner compared with a 12 hour film. Based on the above information, a new mechanism for antiwear film formation is proposed.

Journal

WearElsevier

Published: Jan 1, 1997

References

  • The composition of surface layers formed in a lubricated cam/tappet contact
    Willermet, P.A.; Pieprzak, J.M.; Dauley, D.P.; Carter, R.O.; Lindsay, N.E.; Haack, L.P.; de Vries, J.E.
  • The composition of lubricant-derived surface layers formed in a lubricated cam/tappet contact, II: effects of adding overbased detergent and dispersant to a simple ZDTP solution
    Willermet, P.A.; Dailey, D.P.; Carter, R.O.; Schmitz, P.J.; Zhu, W.; Bell, J.C.; Park, D.
  • Chemical characterization of tribochemical films using X-ray absorption spectroscopy
    Kasrai, M.; Yin, Z.; Bancroft, G.M.; Laycock, K.F.; Tan, K.H.; Feng, X.H.
  • Sampling depth of total electron and fluorescence measurements in Si L-edge and K-edge absorption spectroscopy
    Kasrai, M.; Lennard, W.N.; Brunner, R.W.; Bancroft, G.M.; Bardwell, J.A.; Tan, K.H.
  • X-ray fluorescence measurements of Si, P and S L-edge
    Kasrai, M.; Yin, Z.; Bancroft, G.M.; Tan, K.H.
  • Ultrasoft (C, N, O) X-ray fluorescence detection: proportional-counters, focusing multilayer mirrors, and scattered-light systematics
    Fischer, D.A.; Colbert, J.; Gland, J.L.
  • The surface chemistry of zinc dialkyldithiophosphate, an antiwear additive, on oxidized iron and steel
    Rhodes, K.L.; Stair, P.C.
  • Mechanism of formation of antiwear films from zinc dialkyldithiophosphates
    Willerment, P.A.; Dailey, D.P.; Carter, R.O.; Schmitz, P.J.; Zhu, W.

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