Dorgham, A, Parsaeian, P orcid.org/0000-0001-8393-3540, Azam, A orcid.org/0000-0002-3510-1333 et al. (5 more authors) (2021) Tribochemistry evolution of DDP tribofilms over time using in-situ synchrotron XAS. Tribology International, 160. 107026. ISSN 0301-679X
Abstract
Ashless dialkyldithiophosphate (DDP) antiwear additives are good candidates to replace the widely used metallic DDPs such as zinc dialkyldithiophosphate (ZDDP), which are less environmentally friendly. A newly designed in-situ tribological rig was utilised to perform in-situ synchrotron X-ray absorption spectroscopy (XAS) in order to examine the decomposition reactions of two types of DDPs; acidic and neutral. The tribological experiments showed that the two DDP additives decomposed to form protective tribofilms on the steel surface, which provided better antiwear protection than ZDDP regardless of the tribofilm thickness. The neutral DDP formed a thinner tribofilm (about 33 nm) than ZDDP (about 41 nm), whereas the tribofilm of the acidic DDP had a much lower thickness (<7 nm) but more superior antiwear protection. The two DDPs also provided lower friction coefficient (<0.1) than the 0.12 provided by ZDDP. The XAS experiments suggest that the DDPs decompose to form initially iron sulphate, which is quickly reduced to sulphide before forming the phosphate layers of the protective tribofilm. These layers consisted initially of iron phosphate of short chains but as rubbing continued organic phosphate with long chains started to form.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | © 2021 Elsevier Ltd. All rights reserved. This is an author produced version of an article published in Tribology International. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | ZDDP; DDP; Antiwear tribofilm; In-situ tribochemistry; Synchrotron XAS |
Dates: |
|
Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Mechanical Engineering (Leeds) > Institute of Functional Surfaces (Leeds) |
Funding Information: | Funder Grant number EPSRC (Engineering and Physical Sciences Research Council) EP/R001766/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 15 Jul 2021 15:13 |
Last Modified: | 02 Apr 2022 00:38 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.triboint.2021.107026 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:176136 |
Download
Filename: Tribochemistry evolution of DDP tribofilms.pdf
Licence: CC-BY-NC-ND 4.0