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Influence of composition and production route on the miscrostructure and precision of cemented carbide products
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
2016 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This master thesis focused on the precision of hardmetal rods after diamond coating, mimicked by annealing. The aim of this study was to determine the importance of the effect of Cobalt (Co) on the lack of precision of the rods, but as a start the process reliability has been tested.

Rods made with the same batch number but with different production numbers have been analyzed and compared by measuring and comparing their mean intercept length and contiguity.

After study, the parameters did not show any consequential changes for the three production numbers. It was then concluded that the production route was stable.

As for the Co-line, four formulations (one non doped, two with various amounts of Chromium (Cr) and one Vanadium (V) doped) were sintered with different conditions (four H2 pre-treatment temperatures (800 °C to 1100 °C) and Hot Isostatic Pressing (HIP) for half of them) in order to influence the Carbon (C) balance of the samples.

This second section showed a certain influence of the type of doping. When compared to non-doped samples, V tend to worsen the precision of the rods while Cr had contradictory results: when added in small amounts (0.05 wt%) it worsened the runout whereas it improved it when added in larger amounts (0.5 wt%). It is possible that some non-representative false results happened in this section. Nevertheless, it is certain that Cr have an impact on the binder state.

HIP treatment improved the final distortion of the rods compared to non-HIP ones. The found explanation is that the grains were subjected to rearrangement during HIP treatment and thus were less likely to move during annealing. In addition, the amount of W dissolved into Co was measured and indicated a change in the binder composition between non-HIP and HIP samples.

 The H2 pre-treatment temperature also had an impact on the precision as it induced several different positions in the carbon window of the products.

Place, publisher, year, edition, pages
2016. , 100 p.
Keyword [en]
cemented carbide, hardmetal
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:ltu:diva-59709OAI: oai:DiVA.org:ltu-59709DiVA: diva2:1034726
External cooperation
Ceratizit
Subject / course
Student thesis, at least 30 credits
Educational program
Materials Engineering, master's level (120 credits)
Supervisors
Examiners
Available from: 2016-10-14 Created: 2016-10-12 Last updated: 2016-12-09Bibliographically approved

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