title: Chemical nature of alkaline polyphosphate boundary film at heated rubbing surfaces.
abstract: Alkaline polyphosphate has been demonstrated to be able to reduce significant wear and friction of sliding interfaces under heavy loads (>1 GPa) and elevated temperature (800 °C and above) conditions, e.g. hot metal manufacturing. The chemical composition and fine structure of polyphosphate lubricating film is not well understood as well as the role of alkaline elements within the reaction film at hot rubbing surface. This work makes use of the coupling surface analytical techniques on the alkaline polyphosphate tribofilm, XANES, TOF-SIMS and FIB/TEM. The data show the composition in gradient distribution and trilaminar structure of tribofilm: a shorter chain phosphate overlying a long chain polyphosphate that adheres onto oxide steel base through a short chain phosphate. The chemical hardness model well explains the anti-abrasive mechanism of alkaline polyphosphate at elevated temperatures and also predicts a depolymerisation and simultaneous cross-linking of the polyphosphate glass. The role of alkaline elements in the lubrication mechanism is especially explained. This work firstly serves as a basis for a detailed study of alkaline polyphosphate tribofilm at temperature over 600 °C.
authors.affiliation: Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong, NSW 2522, Australia.
authors.forename: Shanhong
authors.initials: S
authors.lastname: Wan
authors.affiliation: Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong, NSW 2522, Australia.
authors.forename: A Kiet
authors.initials: AK
authors.lastname: Tieu
authors.affiliation: Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong, NSW 2522, Australia.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong, NSW 2522, Australia.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong, NSW 2522, Australia.
authors.forename: Shaogang
authors.initials: S
authors.lastname: Cui
authors.affiliation: Electron Microscopy Centre, University of Wollongong, Wollongong, NSW 2522, Australia.
authors.forename: David R G
authors.initials: DR
authors.lastname: Mitchell
authors.affiliation: Electron Microscope Unit, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Charlie
authors.initials: C
authors.lastname: Kong
authors.affiliation: Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168, Australia.
authors.forename: Bruce
authors.initials: B
authors.lastname: Cowie
authors.affiliation: Future Industries Institute, University of South Australia, Mawson Lakes SA 5095, Australia.
authors.forename: John A
authors.initials: JA
authors.lastname: Denman
authors.affiliation: Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Crawley, Australia.
authors.forename: Rong
authors.initials: R
authors.lastname: Liu