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Reduction in Wear Rate of α-Alumina and Silicon Nitride by Diffusional Surface Modification

Published online by Cambridge University Press:  28 February 2011

A.K. Gangopadhyay ,
M.E. Fine  and
H.S. Cheng
A.K. Gangopadhyay
Affiliation:
Center for Engineering Tribology Northwestern University, Evanston, IL 60208
M.E. Fine
Affiliation:
Center for Engineering Tribology Northwestern University, Evanston, IL 60208
H.S. Cheng
Affiliation:
Center for Engineering Tribology Northwestern University, Evanston, IL 60208
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Abstract

The surface regions of α-alumina and hot pressed silicon nitride were modified by suitable alloying in order to improve their wear resistance. The surface modification in polycrystalline α-alumina was done by diffusing chromia into the surface region which resulted in the formation of a thin layer of A12O3 - Cr9O3 solid solution which has a lower thermal expansion coefficient than pure α-alumina. Also Cr2O3 has a larger lattice parameter than α-alumina thus during cooling the surface was put into compression. The surface region of hot pressed silicon nitride was modified by diffusing α-alumina into the surface which resulted in the formation of a thin sialon layer. A surface compressive stress was again introduced due to the lower thermal expansion coefficient and larger latticeparameter of sialon compared to silicon nitride.

Wear tests were conducted against 52100 steel under both lubricated and unlubricated sliding contact using a block on ring apparatus. The wear resistance of chromia surface alloyed α-alumina was improved considerably over unalloyed α-alumina under both lubricated and unlubricated conditions. The wear resistance of alumina surface alloyed silicon nitride was also improved over unalloyed silicon nitride under both lubricated and unlubricated conditions.

Different wear modes were identified by examining the worn surfaces under the scanning electron microscope.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 140: Symposium S – New Materials Approaches to Tribology: Theory and Applications , 1988 , 293
Copyright
Copyright © Materials Research Society 1989

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References

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