Issue 59, 2018

In situ synchrotron XAS study of the decomposition kinetics of ZDDP triboreactive interfaces

Abstract

One of the major obstacles in replacing the widely used zinc dialkyldithiophosphate (ZDDP) antiwear additive with a more environmentally friendly one is the difficulty of time-resolving the surface species resulting from its decomposition mechanism under high contact pressure and temperature. To tackle this issue, a newly developed miniature pin-on-disc tribotester was coupled with synchrotron X-ray absorption spectroscopy (XAS) to perform in situ tribological tests while examining the composition of the formed triboreactive films. The results showed that in the case of bare steel surfaces the initial decomposition products are mainly zinc sulfate species, which with further shearing and heating are reduced to zinc sulfide mixed with metal oxides. The mixed base layer seems to enhance the tenacity of the subsequently formed zinc phosphate layers composing the main bulk of the protective triboreactive film. This base layer was not observed in the case of coated substrates with hydrogenated diamond-like carbon (a-C:H DLC) coating, which results in the formation of less durable films of small volume barely covering the contacting surfaces and readily removed by shear. Comprehensive decomposition pathways and kinetics for the ZDDP triboreactive films are proposed, which enable the control and modification of the ZDDP triboreactive films.

Graphical abstract: In situ synchrotron XAS study of the decomposition kinetics of ZDDP triboreactive interfaces

Article information

Article type
Paper
Submitted
04 Jun 2018
Accepted
22 Sep 2018
First published
04 Oct 2018
This article is Open Access
Creative Commons BY-NC license

RSC Adv., 2018,8, 34168-34181

In situ synchrotron XAS study of the decomposition kinetics of ZDDP triboreactive interfaces

A. Dorgham, P. Parsaeian, A. Neville, K. Ignatyev, F. Mosselmans, M. Masuko and A. Morina, RSC Adv., 2018, 8, 34168 DOI: 10.1039/C8RA04753G

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