Abstract

The loss of energy due to friction is one of the major problems industries are facing nowadays. Friction reduces the mechanical efficiency of the machine components. It is estimated that an average of 40% energy is lost to overcome the friction. In recent years, surface modification and surface texturing have shown tremendous ability to reduce friction and wear. Microstructures generated on the surface act as a secondary reservoir for lubricants and wear particle receptacles to reduce further abrasion. In addition, surface texturing boost hydrodynamic pressure which increases the elasto-hydrodynamic lubrication regime of the Stribeck curve, reducing friction and wear. There are different techniques used to texture the surfaces such as sandblasting, acid etching, laser texturing, modulation-assisted machining, etc. Amongst all these techniques, laser texturing is the most popular due to its advantages like high accuracy, good consistency and celerity as compared to other techniques. This study focuses on the effects of laser texturing on tribological properties of titanium alloy Ti6Al4V when in contact with a tungsten carbide ball. The effect of varying the dimple density on friction is studied using PAO as a lubricant in titanium-tungsten carbide contact. Tests were performed on 8 samples with different dimple densities and on an untextured sample. These different dimple densities were achieved by using different laser speeds. Increasing in the laser speed results in a decrease in the dimple density. Results showed that friction, as well as wear, is reduced for all the textured samples as compared to an untextured sample. For the two samples with the highest dimple densities and laser speeds of 400mm/s and 800mm/s, friction is reduced by 67% as compared to untextured surface. However, for the sample with laser speed of 400mm/s and dimple density of 50dimples/mm the surface hardness is increased considerably due to a longer exposure to laser, which can affect the tribological properties of the material. The second sample with laser speed of 800mm/s and dimple density of 25dimples/mm shows very low increase in surface hardness and it can be said that the reduction in friction is the effect of laser texturing. For other samples with intermediate dimple densities and laser speeds from 1200mm/s to 2800mm/s, the friction coefficient stays low until the dimples wear out from the surface and then increases to a value similar to the friction coefficient of untextured surface. Overall, the texturing of the metal surface improves tribological properties of the metal.

Library of Congress Subject Headings

Surfaces (Technology); Titanium alloys--Surfaces; Ceramics--Surfaces; Tribology

Publication Date

7-2020

Document Type

Thesis

Student Type

Graduate

Degree Name

Mechanical Engineering (MS)

Department, Program, or Center

Mechanical Engineering (KGCOE)

Advisor

Patricia Iglesias Victoria

Advisor/Committee Member

Michael Schertzer

Advisor/Committee Member

Rui Liu

Campus

RIT – Main Campus

Plan Codes

MECE-MS

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