Wear and friction of self-lubricating CuO-TZP composites

Mahdiar Valefi

Research output: ThesisPhD Thesis - Research UT, graduation UT

Abstract

In certain applications, including high temperature or vacuum environments, liquid lubricants or greases are not stable. Solid lubricants are potentially suitable candidates for the reduction of friction and wear. Ceramic materials are a suitable candidate for harsh environments such as high temperatures and vacuum. Ceramic components are generally lubricated by thin solid films to achieve low friction and wear. The lifetime of such films is inevitably limited. By incorporating solid lubricant reservoirs into a hard ceramic matrix, friction and wear can be decreased during sliding by realizing a gradual replenishment of the soft solid lubricant to the surface. Therefore, it is of great importance to study the self-lubricating ability of the ceramic contact. In this thesis, a CuO doped zirconia composite has been chosen as a self-lubricating ceramic composite system. The tribological performance of the ceramic composite has been systematically investigated. To understand the self-lubricating ability of the composite, the friction behaviour has been studied at different temperature levels. First, dry sliding tests were conducted at room temperature using different loads and sliding velocities as well as countersurfaces. The wear mechanisms have been investigated using different characterization methods. At room temperature, 5CuO-TZP only shows low friction and wear against an alumina countersurface. Similar dry sliding tests have been carried out at elevated temperatures. A coefficient of friction of 0.35 and a specific wear rate less than 10-6 mm3/Nm were obtained at 600 °C for CuO-TZP sliding against an alumina countersurface. It has been found that a soft copper rich (third body) layer is formed at the interface between the sliding components. The formation of the soft layer as well as the wear mechanism has been explained. A physically-based model has been developed which includes the processes responsible for maintaining the soft third body layer at the interface. The model can predict the thickness of the third body layer under different tribological conditions in the mild wear regime. It can be concluded that the tribological performance of CuO-TZP under dry contact conditions strongly depends on the operational conditions.
Original languageEnglish
Awarding Institution
  • University of Twente
Supervisors/Advisors
  • Schipper, Dirk J., Supervisor
  • de Rooij, Matthias B., Advisor
Award date21 Sep 2012
Place of PublicationEnschede
Publisher
Print ISBNs9789036534093
DOIs
Publication statusPublished - 21 Sep 2012

Fingerprint

Wear of materials
Friction
Composite materials
Solid lubricants
Alumina
Temperature
Vacuum
High temperature applications
Lubricating greases
Ceramic materials
Zirconia
Lubricants
Large scale systems
Copper
Liquids

Keywords

  • Onderzoek van algemene industriele aardMechanical engineering and technologyProduktie- en procestechnieken
  • METIS-288153
  • IR-81500

Cite this

Valefi, Mahdiar. / Wear and friction of self-lubricating CuO-TZP composites. Enschede : University of Twente, 2012.
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title = "Wear and friction of self-lubricating CuO-TZP composites",
abstract = "In certain applications, including high temperature or vacuum environments, liquid lubricants or greases are not stable. Solid lubricants are potentially suitable candidates for the reduction of friction and wear. Ceramic materials are a suitable candidate for harsh environments such as high temperatures and vacuum. Ceramic components are generally lubricated by thin solid films to achieve low friction and wear. The lifetime of such films is inevitably limited. By incorporating solid lubricant reservoirs into a hard ceramic matrix, friction and wear can be decreased during sliding by realizing a gradual replenishment of the soft solid lubricant to the surface. Therefore, it is of great importance to study the self-lubricating ability of the ceramic contact. In this thesis, a CuO doped zirconia composite has been chosen as a self-lubricating ceramic composite system. The tribological performance of the ceramic composite has been systematically investigated. To understand the self-lubricating ability of the composite, the friction behaviour has been studied at different temperature levels. First, dry sliding tests were conducted at room temperature using different loads and sliding velocities as well as countersurfaces. The wear mechanisms have been investigated using different characterization methods. At room temperature, 5CuO-TZP only shows low friction and wear against an alumina countersurface. Similar dry sliding tests have been carried out at elevated temperatures. A coefficient of friction of 0.35 and a specific wear rate less than 10-6 mm3/Nm were obtained at 600 °C for CuO-TZP sliding against an alumina countersurface. It has been found that a soft copper rich (third body) layer is formed at the interface between the sliding components. The formation of the soft layer as well as the wear mechanism has been explained. A physically-based model has been developed which includes the processes responsible for maintaining the soft third body layer at the interface. The model can predict the thickness of the third body layer under different tribological conditions in the mild wear regime. It can be concluded that the tribological performance of CuO-TZP under dry contact conditions strongly depends on the operational conditions.",
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doi = "10.3990/1.9789036534093",
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Wear and friction of self-lubricating CuO-TZP composites. / Valefi, Mahdiar.

Enschede : University of Twente, 2012.

Research output: ThesisPhD Thesis - Research UT, graduation UT

TY - THES

T1 - Wear and friction of self-lubricating CuO-TZP composites

AU - Valefi, Mahdiar

PY - 2012/9/21

Y1 - 2012/9/21

N2 - In certain applications, including high temperature or vacuum environments, liquid lubricants or greases are not stable. Solid lubricants are potentially suitable candidates for the reduction of friction and wear. Ceramic materials are a suitable candidate for harsh environments such as high temperatures and vacuum. Ceramic components are generally lubricated by thin solid films to achieve low friction and wear. The lifetime of such films is inevitably limited. By incorporating solid lubricant reservoirs into a hard ceramic matrix, friction and wear can be decreased during sliding by realizing a gradual replenishment of the soft solid lubricant to the surface. Therefore, it is of great importance to study the self-lubricating ability of the ceramic contact. In this thesis, a CuO doped zirconia composite has been chosen as a self-lubricating ceramic composite system. The tribological performance of the ceramic composite has been systematically investigated. To understand the self-lubricating ability of the composite, the friction behaviour has been studied at different temperature levels. First, dry sliding tests were conducted at room temperature using different loads and sliding velocities as well as countersurfaces. The wear mechanisms have been investigated using different characterization methods. At room temperature, 5CuO-TZP only shows low friction and wear against an alumina countersurface. Similar dry sliding tests have been carried out at elevated temperatures. A coefficient of friction of 0.35 and a specific wear rate less than 10-6 mm3/Nm were obtained at 600 °C for CuO-TZP sliding against an alumina countersurface. It has been found that a soft copper rich (third body) layer is formed at the interface between the sliding components. The formation of the soft layer as well as the wear mechanism has been explained. A physically-based model has been developed which includes the processes responsible for maintaining the soft third body layer at the interface. The model can predict the thickness of the third body layer under different tribological conditions in the mild wear regime. It can be concluded that the tribological performance of CuO-TZP under dry contact conditions strongly depends on the operational conditions.

AB - In certain applications, including high temperature or vacuum environments, liquid lubricants or greases are not stable. Solid lubricants are potentially suitable candidates for the reduction of friction and wear. Ceramic materials are a suitable candidate for harsh environments such as high temperatures and vacuum. Ceramic components are generally lubricated by thin solid films to achieve low friction and wear. The lifetime of such films is inevitably limited. By incorporating solid lubricant reservoirs into a hard ceramic matrix, friction and wear can be decreased during sliding by realizing a gradual replenishment of the soft solid lubricant to the surface. Therefore, it is of great importance to study the self-lubricating ability of the ceramic contact. In this thesis, a CuO doped zirconia composite has been chosen as a self-lubricating ceramic composite system. The tribological performance of the ceramic composite has been systematically investigated. To understand the self-lubricating ability of the composite, the friction behaviour has been studied at different temperature levels. First, dry sliding tests were conducted at room temperature using different loads and sliding velocities as well as countersurfaces. The wear mechanisms have been investigated using different characterization methods. At room temperature, 5CuO-TZP only shows low friction and wear against an alumina countersurface. Similar dry sliding tests have been carried out at elevated temperatures. A coefficient of friction of 0.35 and a specific wear rate less than 10-6 mm3/Nm were obtained at 600 °C for CuO-TZP sliding against an alumina countersurface. It has been found that a soft copper rich (third body) layer is formed at the interface between the sliding components. The formation of the soft layer as well as the wear mechanism has been explained. A physically-based model has been developed which includes the processes responsible for maintaining the soft third body layer at the interface. The model can predict the thickness of the third body layer under different tribological conditions in the mild wear regime. It can be concluded that the tribological performance of CuO-TZP under dry contact conditions strongly depends on the operational conditions.

KW - Onderzoek van algemene industriele aardMechanical engineering and technologyProduktie- en procestechnieken

KW - METIS-288153

KW - IR-81500

U2 - 10.3990/1.9789036534093

DO - 10.3990/1.9789036534093

M3 - PhD Thesis - Research UT, graduation UT

SN - 9789036534093

PB - University of Twente

CY - Enschede

ER -