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Wear mechanisms of wedge-shaped hardmetals abraded by SiC grits at various loads
2005 (English)Independent thesis Advanced level (degree of Master (One Year))Student thesis
Abstract [en]

Since quite long time ago, the WC-Co grades were found to be the best composite for cutting technology due to a combination of high hardness and reasonable fracture toughness. Even if the WC compound is not supposed to be the hardest material, and Co is quite a ductile material, a combination of them gives a best fit in tribological application. It is known that the renowned tribologicial properties of hard metals are due to their, microstructural characteristics. Especially in the cutting tool industry, WC-Co materials play an important role in achieving high cutting speeds, better surface finishing and improved productivity. In the cutting tool industry, abrasive wears is the common failure mode in WC-Co tools. Although many physically based models of abrasive wear of WC-Co composites have been created, all the models are based on abrading a flat specimen. On contrary, the real situation looks rather like interaction of a wedge-shaped specimen with abrasive particles, which are embedded in to the matrix. Therefore, in the present research, a two body abrasive test scheme was employed for testing of wedge-shaped WC-Co specimens. Dependence of wear volume on sliding distance, influence of abrasive size and load on wear mechanisms operative were investigated. Six grades of WC-Co composites ranging from coarse grade to nanostructured composite were selected. SiC abrasive particles of 4000 and 80 grit were used. It has been found that for coarse grades slid along 4000 paper, a wear diagram consists of two portions, further called unsteady and steady stages. Fracturing and pullout of WC grains was found the predominant wear mechanism at the initial stage, while plastic deformation (grooving) is the main at steady stages. In case of nanoscale materials, plowing was founds as the main wear mechanism at all stages, that provided higher volumetric wear compared to coarse grades. Increase in grit size as well as load from 2N to 15N led to initiation of chipping at the beginning stages. Further wear nevertheless, was identified as plowing, independently on WC grain size and binder content. Features of wear mechanisms observed were discussed related to abrasive grit size and microstructure of the materials investigated.

Place, publisher, year, edition, pages
2005. , 72 p.
Identifiers
URN: urn:nbn:se:kau:diva-57216Local ID: MTK D-4OAI: oai:DiVA.org:kau-57216DiVA: diva2:1121819
Subject / course
Mechanical Engineering
Available from: 2017-07-12 Created: 2017-07-12

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  • apa
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  • ieee
  • modern-language-association-8th-edition
  • vancouver
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Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
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  • nn-NB
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  • Other locale
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