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Hot wear testing of spray formed hot work steels for aluminium extrusion
2004 (English)Independent thesis Advanced level (degree of Master (One Year))Student thesis
Abstract [sv]

Spray forming is a relatively modern method for production of tool steels and commercial plants have been in use since the mid-eighties. This method is more economical and less time demanding than powder metallurgical production. It also results in better mechanical properties than the tool material made by traditional casting and, like the powder materials, is free from segregation on macro level. The spray forming of tool steels is a relatively new method for production of modern steels. This method involves features of casting and powder metallurgy methods. Because of the high solidification rate, billets formed by spray forming contain coarser carbides compared to the powder process, because of microsegregation. This is especially important for tool steels, for instance for aluminum extrusion applications. At aluminum extrusion, the aluminum is heated to be soft but not molten and pressed through one or several die openings. During exploitation, the extrusion die suffers by high temperature and mechanical contact which will lead to significant wear. Abrasion, adhesion, chemical reacting and delamination are main observed operative wear mechanisms. The dies are normally made of hot work tool steel, H13. To increase the wear resistance surface treatment by nitriding, nitrocarburizing or coating approaches are in use. In this research work, a comparative study of wear resistance of spray formed Toughtec, powder metallurgy prepared CPM9V and nitrocarburized Orvar 2M tool steels was carried out. The tests were performed on a block-on-cylinder equipment at 450°C in an argon atmosphere to simulate aluminum extrusion conditions. AA7075 age hardened alloy was used as a counterface (cylinder). The influence of microstructure, especially carbides shape and distribution, on wear mechanisms and rates were of high interest. The wear mechanisms appearing in the specimens without surface treatment was abrasion wear in combination with adhesive wear. For the specimens with nitrocarburized surface the main mechanism was delamination wear. The worn volume for the untreated materials was quite high almost similar for both powder material and spray formed steels. The Orvar 2M material with a nitrocarburized surface showed a worn volume about five times higher than spray formed and powder metallurgy specimens. A significant influence of nitrocarburizing of spray formed material on wear resistance was not observed.

Place, publisher, year, edition, pages
2004. , p. 48
Identifiers
URN: urn:nbn:se:kau:diva-57213Local ID: MTK D-2OAI: oai:DiVA.org:kau-57213DiVA, id: diva2:1121816
Subject / course
Mechanical Engineering
Available from: 2017-07-12 Created: 2017-07-12

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CiteExportLink to record
Permanent link

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Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf