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Title: Tribology of advanced metallic materials
Keywords: Wear Mechanisms, MMCs, DMD, Mg-Nip ,Mg-Cup and Mg-Tip
Issue Date: 6-Jan-2005
Citation: SHANTHI MUTHUSAMY (2005-01-06). Tribology of advanced metallic materials. ScholarBank@NUS Repository.
Abstract: The aim of this project is to investigate the tribological characteristics of magnesium-based composites reinforced with different types of metallic particulates. Three different groups of composites; namely, magnesium-nickel, magnesium-copper and magnesium-titanium, denoted as Mg-Nip ,Mg-Cup and Mg-Tip, with volume fractions ranging from 1.5-6.1% for nickel, 2.1-6.6 % for copper, and 2.2-5.9% for titanium, along with pure magnesium, were tested using a pin-on-disc wear tester under dry sliding conditions to study the effects of sliding speed, normal load and particulate content on the wear performance of the composites. Experimental results revealed that an increase in normal load from 10N to 30N resulted in increased wear rates for both pure magnesium and its composites. An increase in sliding speed also generally resulted in increased wear rates. For each of the sets of composites, an optimum particulate content for improved wear performance was found. Under the low sliding speeds both the copper-reinforced and titanium-reinforced composites showed better wear performance but as the sliding speed is increased, the nickel-reinforced composites were better. Under the most severe sliding condition, the nickel-reinforced composites exhibited up to 9-fold increase in wear resistance than pure magnesium and up to 6-fold improvement over other composites. Five different wear mechanisms; namely, oxidation, abrasion, adhesion, delamination and melt wear were found to be operative under various sliding conditions. Oxidation wear was the dominant wear mechanism observed under mild sliding conditions for all specimens except for titanium-reinforced composites. Under mild sliding conditions, a stable oxide layer is formed on the pin surface which offered better protection against metal-metal contact especially in Mg-Cu composites, which had the best performance. Abrasive wear is dominant under mild to moderate sliding conditions for all specimens. The composites exhibited lower wear rates than pure magnesium due to their better hardness. Fatigue-related wear (delamination) is also observed under moderate sliding conditions for the composites only. However, the composites showed superior wear performance despite the delamination because the pure magnesium had already begun to wear by the more severe process of adhesion. Adhesion is also operative under moderate to severe sliding conditions for the composites. It is generally less extensive in composites once again due to their high hardness. Melt wear is observed mainly in pure magnesium. The composites are able to withstand this wear mechanism because the hard particulates reduced the true contact area between pin and disc, thus lessening the frictional heating during sliding. Based on the wear mechanisms and wear rates obtained, the magnesium-based composites reinforced with metallic particulates, particularly the nickel-reinforced composites are recommended for an application where light weight and better wear resistance is an important criterion.
Appears in Collections:Master's Theses (Open)

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