A study on the wear and wear transitions of ceramics. Ph.D. Thesis

Thesis/Dissertation · Sat Jan 01 04:00:00 EST 1994

OSTI ID:218160

Wang, Y

A critical literature review reveals many phenomenological observations with respect to wear of ceramics. Conclusions vary and sometimes contradict one another. No clear picture has emerged with respect to ceramic wear levels and wear mechanisms. Wear models usually fail to take into account the microstructural effects and the presence of wear transitions. This lack of predictive models hinders the tribological applications of ceramics. In this study, wear, wear mechanisms, and wear transitions of ceramics were systematically studied by indentation, inclined plane scratch, and wear tests under a variety of load, speed, and lubrication conditions. Deformation, tribochemical, microcrack, and microfracture controlled wear mechanisms were found. Two and three dimensional wear diagrams and wear transition/mechanism maps were developed for several ceramics to visualize the relationship of wear and the operating parameters. These maps and diagrams will facilitate the design and application of these materials. The tensile stress trajectory along the sliding direction was found to coincide with the observed crack patterns from the scratch and wear tests. The maximum tensile stress at the rear edge of the contact was the predominant stress which caused the cracks to propagate. For the ceramics studied, the stress at which the crack propagated coincided with the occurrence of the wear transition. The tensile stresses for a Hertzian contact was calculated by using the Hamilton`s equations. The ratio of the maximum tensile stress to the critical external damage stress was found to be the key parameter affecting the wear transitions. Finally, a predictive wear model for ceramics was developed. The correlation of the model with the experimental data of alumina and silicon nitride shows agreement. The distinctive features of this simplistic model are its ability to predict the wear transitions as well as to estimate the level of wear for the ceramics studied.

• Research Organization: Maryland Univ., College Park, MD (United States)
• OSTI ID: 218160
• Report Number(s): N--96-21357; NIPS--96-33280
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
CERAMICS
CRACK PROPAGATION
MATHEMATICAL MODELS
MICROSTRUCTURE
SILICON NITRIDES
TRIBOLOGY
WEAR