Degree Name

Master of Science (MS)

Semester of Degree Completion

1996

Thesis Director

Ping Liu

Abstract

Electrotribological and arc erosion behavior of Cu-15vol.%Cr in situ composite was investigated in terms of coefficient of friction, interfacial resistance, bulk temperature, and wear rate as a function of normal pressure, sliding speed, and electrical current. Microstructural change due to electrical sliding was studied to understand wear mechanisms. Cu-15vol.%Cr in situ composite was selected in this research because it exhibits an excellent combination of mechanical strength and electrical/thermal conductivity.

It was found that the average coefficient of friction decreased with increasing electrical current under dry electrical sliding. The average coefficient of friction was lower under lubricated electrical sliding than that under dry electrical sliding, but it increased with increasing electrical current. There are no significant effects of normal pressure and sliding speed on coefficient of friction under dry electrical sliding. Under lubricated electrical sliding, the coefficient of friction decreased with increasing normal pressure, but it did not change significantly with sliding speed.

Both static and dynamic interfacial resistance decreased slightly with increasing normal pressure and the dynamic interfacial contact resistance decreased with increasing electrical current. The openness of circuit decreased with increasing normal pressure, increased with increasing sliding speed, and electrical current. The bulk temperature increased with increasing electrical current for both dry and lubricated electrical sliding.

The non-electrical wear rate of the composite increased with increasing normal pressure and decreased with increasing sliding speed. The electrical wear rate decreased with increasing electrical current under dry electrical sliding, whereas the wear rate increased with increasing electrical current under lubricated electrical sliding. The effects of normal pressure and sliding speed on the wear rate of the composite under both dry and lubricated electrical sliding are dependent upon the level of electrical current.

The sliding-induced subsurface deformation occurred not only in the sliding direction but also in the lateral directions perpendicular to the sliding direction. The complex deformation mode was revealed clearly by the morphological change of the ribbon-like filaments. The thickness of the subsurface deformation layer increased with increasing normal pressure and sliding speed under dry non-electrical sliding. The thickness of the subsurface deformation layer decreased with increasing electrical current under dry electrical sliding, whereas the thickness increased with increasing electrical current under lubricated electrical sliding. A hardened surface layer and less damage on the subsurface layer were accounted for reduction in wear rate as electrical current was applied.

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