Studies on ZDDP Anti-Wear Films Formed Under Different Conditions by XANES Spectroscopy, Atomic Force Microscopy and 31P NMR

Antiwear (AW) films, generated from a mineral base oil containing a zinc dialkyl dithiophosphate (ZDDP) additive, were studied as a function of formation temperature, load and rubbing time. The surface morphology of these films was investigated using atomic force microscopy (AFM), and surface roughness calculated for the observed differing surface morphologies. The morphology of the films is heterogeneous for all the tested conditions, but the surface roughness is dependent on the rubbing condition. X-ray absorption near edge structure (XANES) spectroscopy has been used to characterize the chemistry of these films, and the intensity of the phosphorus K-edge was also used to monitor their thickness. The thickness of these films is in the range of 10–90 nm depending on the running conditions. Phosphorus L-edge spectra show that these films have a similar chemical nature with variable polyphosphate chain-lengths. 31P NMR was used to study the decomposition of ZDDP in the residual oils. The spectra show that the primary and secondary ZDDP react differently under the various conditions. The tribological characteristics of these AW films were probed by measuring the coefficients of friction (μ) and the wear scar width (WSW) of the counter faces. μ is highly related to the applied load and the results of WSW measurements show that the wear performance is related to all the tested parameters, temperature, load and rubbing time.

[1]  R. Sarin,et al.  Sulphur-phosphous components in gear oils: part 1, oxidation stability studies by 31P-NMR spectroscopic techniques , 2002 .

[2]  Yang-Tse Cheng,et al.  Chemical and Mechanical Properties of ZDDP Antiwear Films on Steel and Thermal Spray Coatings Studied by XANES Spectroscopy and Nanoindentation Techniques , 2003 .

[3]  P. Ryason,et al.  X-Ray Absorption Study of the Effect of Calcium Sulfonate on Antiwear Film Formation Generated From Neutral and Basic ZDDPs: Part 1—Phosphorus Species , 2003 .

[4]  M. Kasrai,et al.  Study of surface films of overbased sulfonates and sulfurized olefins by X-Ray Absorption Near Edge Structure (XANES) spectroscopy , 2006 .

[5]  P. A. Willermet,et al.  Mechanism of formation of antiwear films from zinc dialkyldithiophosphates , 1995 .

[6]  I. R. Barkshire,et al.  Multi-spectral scanning Auger microscopy of tribological surfaces , 1995 .

[7]  M. M. Francisco,et al.  Antiwear Film Formation by ZnDTP, Detergent, and Dispersant Components of Passenger Car Motor Oils—Part II: Effects of Low-Molecular-Weight Dispersant on Film Formation , 2004 .

[8]  G. Bancroft,et al.  The use of X‐ray absorption spectroscopy for monitoring the thickness of antiwear films from ZDDP , 2000 .

[9]  Mark A. Nicholls,et al.  Review ofthe lubrication ofmetallic surf aces by zinc dialkyl-dithiophosphates , 2005 .

[10]  P. Norton,et al.  Chemical characterization and nanomechanical properties of antiwear films fabricated from ZDDP on a near hypereutectic Al–Si alloy , 2005 .

[11]  Chemomechanical Properties of Antiwear Films Using X-ray Absorption Microscopy and Nanoindentation Techniques , 2004 .

[12]  J. Sheasby,et al.  The effect of steel hardness on the performance of antiwear additives , 1996 .

[13]  R. C. Coy,et al.  Relationship between mechanical properties and structures of zinc dithiophosphate anti–wear films , 1999, Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[14]  M. S. Fuller,et al.  Solution decomposition of zinc dialkyl dithiophosphate and its effect on antiwear and thermal film formation studied by X-ray absorption spectroscopy , 1998 .

[15]  M. C. Jain,et al.  Additive–additive interaction: an XPS study of the effect of ZDDP on the AW/EP characteristics of molybdenum based additives , 2002 .

[16]  S. Jahanmir.  Wear Reduction and Surface Layer Formation by a ZDDP Additive , 1987 .

[17]  M. S. Fuller,et al.  Mechanisms of tribochemical film formation: stabilityof tribo- and thermally-generated ZDDP films , 1997 .

[18]  E. Yamaguchi,et al.  Interaction of ZDDP with Borated Dispersant Using XANES and XPS , 2004 .

[19]  T. Selby,et al.  Analysis of the Volatiles Generated During the Selby-Noack Test by 31 P NMR Spectroscopy , 2005 .

[20]  H. Spikes,et al.  Friction and Wear Behavior of Zinc Dialkyldithiophosphate Additive , 2000 .

[21]  Feng,et al.  X-ray-absorption spectroscopic studies of sodium polyphosphate glasses. , 1995, Physical review. B, Condensed matter.

[22]  J. M. Martín,et al.  A multi-technique approach of tribofilm characterisation , 2004 .

[23]  Tom K Woo,et al.  Molecular Mechanisms for the Functionality of Lubricant Additives , 2005, Science.

[24]  E. Yamaguchi,et al.  Tribofilms generated from ZDDP and DDP on steel surfaces: Part 1, growth, wear and morphology , 2005 .

[25]  C. McCague,et al.  Topography and nanomechanical properties of tribochemical films derived from zinc dialkyl and diaryl dithiophosphates , 1999 .

[26]  A. Lachenwitzer,et al.  Studies on ZDDP Thermal Film Formation by XANES Spectroscopy, Atomic Force Microscopy, FIB/SEM and 31P NMR , 2008 .

[27]  Hugh Spikes,et al.  The History and Mechanisms of ZDDP , 2004 .

[28]  J. M. Martín,et al.  Chemistry of ZDDP Tribofilm by ToF-SIMS , 2004 .

[29]  J. H. Green,et al.  ZDDP and MoDTC interactions and their effect on tribological performance – tribofilm characteristics and its evolution , 2006 .

[30]  Tan,et al.  Si L- and K-edge x-ray-absorption near-edge spectroscopy of gas-phase Si(CH3)x(OCH3)4-x: Models for solid-state analogs. , 1993, Physical review. B, Condensed matter.

[31]  H. Spikes.  Origins of the friction and wear properties of antiwear additives , 2006 .

[32]  N. Spencer,et al.  Surface analytical studies of surface-additive interactions, by means of in situ and combinatorial approaches , 2004 .

[33]  S. Bec,et al.  The two-layer structure of Zndtp tribofilms: Part I: AES, XPS and XANES analyses , 2001 .

[34]  M. S. Fuller,et al.  Application of soft X-ray absorption spectroscopy in chemical characterization of antiwear films generated by ZDDP Part I: the effects of physical parameters , 1997 .

[35]  Masoud Kasrai,et al.  Chemical characterization of antiwear films generated on steel by zinc dialkyl dithiophosphate using X-ray absorption spectroscopy , 1993 .

[36]  J. Loubet,et al.  Temperature Effects on Mechanical Properties of Zinc Dithiophosphate Tribofilms , 2006, physics/0611026.

[37]  T. Michalske,et al.  Nanomechanical properties of films derived from zinc dialkyldithiophosphate , 1998 .

[38]  Lai Gui Yu,et al.  Effects of Mo-Containing Dispersants on the Function of ZDDP: Chemistry and Tribology , 2007 .

[39]  N. Mosey,et al.  A quantum chemical study of the unimolecular decomposition mechanisms of zinc dialkyldithiophosphate antiwear additives , 2004 .