Research Papers: Gas Turbines: Coal, Biomass, and Alternative Fuels

High-Performance Lead-Free Electroplated Composite Bearing Overlay for Heavy Duty Applications

[+] Author and Article Information
Roger Gorges

MAHLE Engine Systems UK Ltd.,
2 Central Park Drive,
Rugby CV23 0WE, UK
e-mail: roger.gorges@gb.mahle.com

Ronald Brock

MAHLE Engine Components USA, Inc.,
23030 MAHLE Drive,
Farmington Hills, MI 48335
e-mail: ronald.brock@us.mahle.com

Contributed by the Coal, Biomass and Alternate Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 13, 2014; final manuscript received February 14, 2014; published online April 18, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(9), 091401 (Apr 18, 2014) (5 pages) Paper No: GTP-14-1082; doi: 10.1115/1.4027197 History: Received February 13, 2014; Revised February 14, 2014

Material selection for engine internal components, e.g., bearings, is becoming increasingly more complex and demanding as the operating environments become more aggressive with the introduction of new technologies for the reduction of CO2 emissions. Historically, engine bearings contained lead, which has excellent fundamental bearing properties such as compatibility (run satisfactorily under conditions of marginal lubrication), conformability (deform and accept small scale geometrical inaccuracies of the crankshaft), and embeddability (tolerance to dirt and other foreign materials) while being readily alloyed to achieve good wear and fatigue resistance. However, facing new challenges, many original equipment manufacturers have started development programs to replace lead-containing with lead-free engine components in order to comply with new end-of-life vehicle directives or anticipated future directives. For more than 15 years, MAHLE has been successfully supplying the light, medium, and heavy duty market, with premium electroplated leaded composite bearings, which are designed to improve wear resistance. Some of this market now demands a switch to lead-free materials, while maintaining or exceeding its aforementioned requirements on bearing material properties. Composites of hard particles in a softer metal matrix are in this context ideally suited bearing materials as they can be tailored to obtain the optimal mix between soft and hard properties for the individual application. Typical hard particles that are commonly used comprise of metal oxides, nitrides or carbides. In addition to higher load carrying capabilities and longer service life, new engine technology trends demand that bearings also must operate under mixed or boundary lubrication conditions without having any adverse effect on the performance and integrity of the engine system. Boundary lubrication is commonly observed upon starting the engine before the elastohydrodynamic oil film is fully established. In this state, load is carried by surface asperities rather than by the lubricant. So far, the incorporation and even distribution of the hard particles into an electroplated lead-free matrix was not achievable using conventional direct current electroplating techniques. MAHLE, therefore, has developed a patented pulse plating technique in order to incorporate hard particles into the overlay metal matrix. The refined and modified crystal structure of the resulting lead-free overlay, with incorporated hard particles, yields a premium electroplated bearing with superior wear and fatigue resistance. Corresponding rig and engine test results have been completed to support the material development.

Copyright © 2014 by ASME
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Fig. 5

Boundary lubricated Viper wear rig

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Fig. 4

Typical structure of a lead-free composite overlay with incorporated particles

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Fig. 3

Schematic pulse diagram

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Fig. 2

Typical structure of the MCB17 lead-free lining material

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Fig. 1

Structure of a trimetallic sliding bearing

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Fig. 6

Results of Viper wear test (after 60 min)

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Fig. 7

Sapphire fatigue rig test setup

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Fig. 8

Set of upper rod bearings before (a) and after (b) 500 h engine test




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