New Functionality of Ionic Liquids as Lubricant Additives: Mitigating Rolling Contact Fatigue

Benjamin C. Stump; Yan Zhou; Huimin Luo; Donovan N. Leonard; Michael B. Viola; Jun Qu

doi:10.1021/acsami.9b10001

New Functionality of Ionic Liquids as Lubricant Additives: Mitigating Rolling Contact Fatigue

Benjamin C. Stump, Yan Zhou, Huimin Luo, Donovan N. Leonard, Michael B. Viola, Jun Qu

Research output: Contribution to journal › Article › peer-review

33 Scopus citations

Abstract

Oil-soluble ionic liquids (ILs) have recently been demonstrated as effective lubricant additives of friction reduction and wear protection for sliding contacts. However, their functionality in mitigating rolling contact fatigue (RCF) is little known. Because of the distinct surface damage modes, different types of surface protective additives often are used in lubricants for sliding and rolling contacts. Therefore, the lubricating characteristics and mechanisms of ILs learned in sliding contacts from the earlier work may not be translatable to rolling contacts. This study explores the feasibility of using phosphonium-phosphate, ammonium-phosphate, and phosphonium-carboxylate ILs as candidate additives in rolling-sliding boundary lubrication, and results suggested that an IL could be either beneficial or detrimental on RCF depending on its chemistry. Particularly, the best-performing phosphonium-phosphate IL at 2% addition made a low-viscosity base oil significantly outperform a more viscous commercial gear oil in reducing the RCF surface damage and associated vibration noise. This IL generated a thicker, smoother, and more homogeneous tribofilm compared with commercial additives, which is likely responsible for the superior RCF protection. Results here suggest good potential for using appropriate IL additives to allow the use of low-viscosity gear and axle fluids for improved efficiency and durability.

Original language	English
Pages (from-to)	30484-30492
Number of pages	9
Journal	ACS Applied Materials and Interfaces
Volume	11
Issue number	33
DOIs	https://doi.org/10.1021/acsami.9b10001
State	Published - Aug 21 2019

Funding

The authors thank J. Dyck and E. Conrad from Cytec Industries for providing phosphonium cation feedstocks, H. Xu from General Motors for discussing real axle lubrication, S. Roy from ORNL for measuring lubricant viscosity, and D. Coffey from ORNL for preparing STEM samples. Research was jointly sponsored by the Vehicle Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy (DOE) and Tank Automotive Research, Development and Engineering Center (TARDEC), U.S. Army, U.S. Department of Defense (DoD). Electron microscopy characterization was in part performed at ORNL’s Center for Nanophase Materials Sciences, sponsored by the Scientific User Facilities Division, Office of DOE-BES. This manuscript has been authored by UT-Battelle, LLC under contract no. DEAC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research by the DOE Public Access Plan (http://energy.gov/downloads/doe-public- access-plan).

Keywords

friction and wear
gear
ionic liquids
lubricant additives
micropitting
rolling contact fatigue

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10.1021/acsami.9b10001

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title = "New Functionality of Ionic Liquids as Lubricant Additives: Mitigating Rolling Contact Fatigue",

abstract = "Oil-soluble ionic liquids (ILs) have recently been demonstrated as effective lubricant additives of friction reduction and wear protection for sliding contacts. However, their functionality in mitigating rolling contact fatigue (RCF) is little known. Because of the distinct surface damage modes, different types of surface protective additives often are used in lubricants for sliding and rolling contacts. Therefore, the lubricating characteristics and mechanisms of ILs learned in sliding contacts from the earlier work may not be translatable to rolling contacts. This study explores the feasibility of using phosphonium-phosphate, ammonium-phosphate, and phosphonium-carboxylate ILs as candidate additives in rolling-sliding boundary lubrication, and results suggested that an IL could be either beneficial or detrimental on RCF depending on its chemistry. Particularly, the best-performing phosphonium-phosphate IL at 2% addition made a low-viscosity base oil significantly outperform a more viscous commercial gear oil in reducing the RCF surface damage and associated vibration noise. This IL generated a thicker, smoother, and more homogeneous tribofilm compared with commercial additives, which is likely responsible for the superior RCF protection. Results here suggest good potential for using appropriate IL additives to allow the use of low-viscosity gear and axle fluids for improved efficiency and durability.",

keywords = "friction and wear, gear, ionic liquids, lubricant additives, micropitting, rolling contact fatigue",

author = "Stump, {Benjamin C.} and Yan Zhou and Huimin Luo and Leonard, {Donovan N.} and Viola, {Michael B.} and Jun Qu",

note = "Publisher Copyright: {\textcopyright} 2019 American Chemical Society.",

year = "2019",

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doi = "10.1021/acsami.9b10001",

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AU - Zhou, Yan

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AU - Leonard, Donovan N.

AU - Viola, Michael B.

AU - Qu, Jun

PY - 2019/8/21

Y1 - 2019/8/21

N2 - Oil-soluble ionic liquids (ILs) have recently been demonstrated as effective lubricant additives of friction reduction and wear protection for sliding contacts. However, their functionality in mitigating rolling contact fatigue (RCF) is little known. Because of the distinct surface damage modes, different types of surface protective additives often are used in lubricants for sliding and rolling contacts. Therefore, the lubricating characteristics and mechanisms of ILs learned in sliding contacts from the earlier work may not be translatable to rolling contacts. This study explores the feasibility of using phosphonium-phosphate, ammonium-phosphate, and phosphonium-carboxylate ILs as candidate additives in rolling-sliding boundary lubrication, and results suggested that an IL could be either beneficial or detrimental on RCF depending on its chemistry. Particularly, the best-performing phosphonium-phosphate IL at 2% addition made a low-viscosity base oil significantly outperform a more viscous commercial gear oil in reducing the RCF surface damage and associated vibration noise. This IL generated a thicker, smoother, and more homogeneous tribofilm compared with commercial additives, which is likely responsible for the superior RCF protection. Results here suggest good potential for using appropriate IL additives to allow the use of low-viscosity gear and axle fluids for improved efficiency and durability.

AB - Oil-soluble ionic liquids (ILs) have recently been demonstrated as effective lubricant additives of friction reduction and wear protection for sliding contacts. However, their functionality in mitigating rolling contact fatigue (RCF) is little known. Because of the distinct surface damage modes, different types of surface protective additives often are used in lubricants for sliding and rolling contacts. Therefore, the lubricating characteristics and mechanisms of ILs learned in sliding contacts from the earlier work may not be translatable to rolling contacts. This study explores the feasibility of using phosphonium-phosphate, ammonium-phosphate, and phosphonium-carboxylate ILs as candidate additives in rolling-sliding boundary lubrication, and results suggested that an IL could be either beneficial or detrimental on RCF depending on its chemistry. Particularly, the best-performing phosphonium-phosphate IL at 2% addition made a low-viscosity base oil significantly outperform a more viscous commercial gear oil in reducing the RCF surface damage and associated vibration noise. This IL generated a thicker, smoother, and more homogeneous tribofilm compared with commercial additives, which is likely responsible for the superior RCF protection. Results here suggest good potential for using appropriate IL additives to allow the use of low-viscosity gear and axle fluids for improved efficiency and durability.

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New Functionality of Ionic Liquids as Lubricant Additives: Mitigating Rolling Contact Fatigue

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