Influence of nanometer scale film structure of ZDDP tribofilm on Its mechanical properties: A computational chemistry study

Tasuku Onodera, Takanori Kuriaki, Yusuke Morita, Ai Suzuki, Michihisa Koyama, Hideyuki Tsuboi, Nozomu Hatakeyama, Akira Endou, Hiromitsu Takaba, Carlos A. Del Carpio, Momoji Kubo, Clotilde Minfray, Jean Michel Martin, Akira Miyamoto

    Research output: Contribution to journalArticlepeer-review

    20 Citations (Scopus)


    We investigated the influence of a nanometer scale film structure of a tribofilm generated from zinc dialkyldithiophosphate (ZDDP) anti-wear additive on its mechanical properties using a combined molecular dynamics (MD) and finite element (FE) method. The frictional behavior of an interface between a native iron oxide layer on steel surface and zinc metaphosphate - regarded as a model material of ZDDP tribofilm - was firstly studied using the MD method. The results showed that the iron atoms in the oxide layer diffused into the phosphate layer during the friction process. The zinc atoms in the phosphate layer also diffused into the oxide layer. Significant interdiffusion of iron and zinc atoms was observed with increasing simulation time. Thus, metallic phosphate with a gradient composition of iron and zinc atoms was formed on the phosphate/oxide interface. We then constructed an axisymmetric nanoindentation simulation model from the MD-derived structures at a certain simulation time and carried out a FE calculation. As a result, we found that the rubbed ZDDP tribofilm, including the phosphate with the gradient composition of metallic atoms, showed larger contact stiffness and hardness. The combined MD/FE simulation indicates that the tribofilm becomes stiffer and harder due to the interdiffusion of iron and zinc atoms on the tribofilm/oxide interface. We have found that the gradient composition formation in ZDDP tribofilm during friction process influences on its mechanical properties.

    Original languageEnglish
    Pages (from-to)976-979
    Number of pages4
    JournalApplied Surface Science
    Issue number4
    Publication statusPublished - Nov 30 2009

    All Science Journal Classification (ASJC) codes

    • General Chemistry
    • Condensed Matter Physics
    • General Physics and Astronomy
    • Surfaces and Interfaces
    • Surfaces, Coatings and Films


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