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Embeddability behaviour of some Pb-free engine bearing materials
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.ORCID iD: 0000-0003-2705-9195
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.ORCID iD: 0000-0003-1162-4671
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.ORCID iD: 0000-0003-1454-1118
2016 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

An important requirement on engine bearing materials is its ability to embed dirt/abrasive particles onto the bearing surface and minimize damage to the expensive crankshaft. This property is achieved by applying an overlay onto the lining. In this work, a journal bearing test rig that operates under steady loading condition has been employed to investigate the embeddability behaviour of selected multi-layered Pb-free engine bearing materials in the presence of contaminant/abrasive particles in engine oil. Test materials include Pb-free bearing materials with overlay compositions of Sn, Bi, PAI containing MoS2 and graphite. Pb-based overlay has also been studied as a reference. Embeddability behaviour in terms of wear and changes in surface topography has been investigated. The damage on the shaft and the bearing surfaces were studied in order to elucidate the mechanisms involved. It has been possible to distinguish between the embeddability characteristics of different materials.

Place, publisher, year, edition, pages
2016.
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
URN: urn:nbn:se:ltu:diva-28440Local ID: 23d64d51-dd27-4755-9e4f-fd0f54f0f2a2OAI: oai:DiVA.org:ltu-28440DiVA, id: diva2:1001637
Conference
STLE Annual Meeting & Exhibition : 15/05/2016 - 19/05/2016
Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-13Bibliographically approved
In thesis
1. Tribological characteristics of some multi-layered Pb-free engine bearing materials
Open this publication in new window or tab >>Tribological characteristics of some multi-layered Pb-free engine bearing materials
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lead (Pb) containing alloys such as white metals and Cu-Pb-Sn (lining) with Pb-based overlay plating have been extensively used as materials for internal combustion engine bearings during the last several decades. However, owing to environmental and health concerns, the use of Pb containing materials in automotive engine components is being restricted. In view of this, attempts are under way to develop and replace Pb-containing materials with Pb–free bearing materials.

The tribological characteristics of these recently developed Pb-free bearing materials have, however, not been fully investigated and only a limited results about their tribological performance are available in open literature. This thesis therefore focuses on investigating the tribological performance of some recently developed Pb-free engine bearing materials. Although engine bearings are designed to operate in full film lubrication conditions yet they also operate in mixed and boundary lubrication regimes where the material properties do affect their tribological performance. There is thus a need to study the tribological behaviour of these new Pb-free bearing materials in mixed and boundary lubrication conditions vis a vis that of conventional Pb-containing bearing linings and overlays. This work has therefore aimed at investigating the tribological characteristics such as friction and wear, seizure behaviour, interaction with different oil formulations and embeddability behaviour of some selected Pb-free engine bearing materials.

Friction and wear properties of Pb-free bearing materials Al-Sn based lining without overlay, bronze lining coated with Polyamide-Imide (PAI) based overlay containing MoS2 and graphite, bronze lining coated with Al-Sn based and PAI based overlay containing MoS2 and graphite, bronze lining coated with Sn-based overlay, and bismuth (Bi) containing bronze lining coated with Sn-based overlay have been studied using a block-on-ring test configuration under unidirectional sliding conditions in mixed and boundary lubrication regimes. The conventional Pb-containing bearing material was also studied as a reference material. Al-Sn based material showed considerably higher friction compared to the other bearing materials. The bearing material with PAI based overlay containing MoS2 and graphite showed superior friction and wear properties compared to all other materials. Sn-based overlay coated materials resulted in comparable friction and wear properties to that of Pbbased overlay. Wear mechanism in Al-Sn based material is mainly adhesive and abrasive in case of Sn based overlay.

Seizure behaviour of the bearing materials were also studied using the block-on-ring test configuration in dry as well as lubricated conditions using pure base oil and a fully formulated engine oil. The PAI based overlay containing MoS2 and graphite showed no sign of seizure even at the highest test load in dry as well as lubricated conditions. Al-Sn based lining without overlay seizes at relatively lower load in dry condition compared to the other bearing materials. Adhesion or wear debris smearing onto the counter surface is the main causes of seizure in dry condition. In lubricated condition, seizure occurred at relatively higher load and the conventional Pb-containing material was found to have better seizure performance compared to the Al-Sn based and Sn-based overlay plated materials.

Tribological compatibility of Pb-free bearing materials with different oil formulations was studied using a ball-on-bearing specimen test configuration in boundary lubrication under reciprocating sliding conditions. Four different bearing materials were investigated using different lubricants with and without oil additives. In general, the bearing materials lubricated with pure PAO base oil showed higher friction compared to those lubricated with oils containing additives. Lubricants containing additives improved wear properties of the bearing materials except in the case of Al-Sn based lining without overlay. It was also observed that the anti-wear additive level did not significantly influence the wear performance of bearing overlays.

The embeddability behaviour of Pb-free bearing materials was studied using a fully formulated engine oil contaminated with SiC particles. Pb-free bearing materials with Snbased overlay, Bi-based overlay, PAI-based overlay containing MoS2 and composite overlay containing PAI, Al, PTFE were investigated. Tests at different rotational speeds (i.e. different oil film thickness) and a constant load were carried out using a journal bearing test rig. It was found that material removal from bearing and shaft surfaces due to abrasive wear is influenced by the lubricant film thickness. The steel counter surface showed lower wear in tests using Sn based overlay and a PAI, Al and PTFE containing composite overlay compared to Bi-based overlay and PAI-based overlay containing MoS2. 

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2017
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-62495 (URN)978-91-7583-847-2 (ISBN)978-91-7583-848-9 (ISBN)
Public defence
2017-05-11, E231, Luleå, 09:00 (English)
Opponent
Available from: 2017-03-20 Created: 2017-03-14 Last updated: 2018-03-13Bibliographically approved

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Gebretsadik, DanielHardell, JensPrakash, Braham

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