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n
2003 (English)Independent thesis Advanced level (degree of Master (One Year))Student thesis
Abstract [en]

Hard metals are a very important group of materials with a wide field of application. One of these is as cutting tools. Hard metals are until now produced by conventional sintering methods. These methods are time consuming and do not allow complex geometries. New methods are required and a prospective technique to utilize instead is Selective Laser Sintering, SLS. In SLS two-component method, a powder mixture of a hard structural phase and a softer matrix phase is fused by a laser. The matrix phase melts and infiltrates the powder bed and binds the particles together. The SLS technique has been used on metals since 1991. But the technique is still not fully developed. Before products can be manufactured for commercial use, further investigations have to be made. Some problems with the sintered materials are that they contain pores and suffer from cracks. In the present research work different chemical compositions and process parameters have been investigated for the SLS of hard metals in order to observe how they affect the porosity, microstructure, hardness and crack density. The results showed that all investigated materials contained pores and cracks. The cracks were of thermal nature and can possibly be explained by excessive energy input during sintering. A model for the crack formation mechanism was suggested based on thermal strains on macro level. Materials design seems to be the best approach to reduce both the crack density and porosity. The hardness of the sintered materials was difficult to measure due to high porosity. But the materials with minimum porosity had hardness values comparable with conventionally manufactured hard metals. Generally, the microstructure was good with a homogeneous distribution of carbides, but in some of the materials, spherical particles were found in the microstructure. These can be explained by an improper ratio of the structural and liquid phase. In order to produce fully dense crack-free hard metals by SLS, more work has to be done. Other material combinations with high-temperature properties are needed and process parameters have to be more carefully selected.

Place, publisher, year, edition, pages
2003. , 67 p.
Identifiers
URN: urn:nbn:se:kau:diva-57200Local ID: MTK D-1OAI: oai:DiVA.org:kau-57200DiVA: diva2:1121803
Subject / course
Mechanical Engineering
Available from: 2017-07-12 Created: 2017-07-12

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