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Liquid phase sintering of W-Ni-Fe composites: liquid penetration, agglomerate separation and tungsten particle growth
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.ORCID iD: 0000-0003-0864-3679
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The initial stage of liquid phase sintering, involving liquid penetration, agglomerate separation, particle spreading and growth has been investigated in experiments using tungsten heavy alloys. The particle composites used were produced by hot isostatic pressing (HIP) of pure powder mixtures of W-Ni-Fe-(Co). By using different HIP temperatures, volume fractions of tungsten, alloying elements like Cobalt and Sulphur or excluding Iron from the matrix, liquid penetration, agglomerate separation and particle growth conditions were affected. The investigations were performed mainly under microgravity (sounding rockets or parabolic trajectories by airplanes) but at high tungsten particle fractions, short sintering times or at infiltration of solid pure tungsten, they were performed at normal gravity. The liquid penetration of the tungsten agglomerates is explained by initial wetting under non-equilibrium conditions, due to the reaction between the liquid matrix and the particles, and a decrease of interfacial energy. The dissolving of tungsten gives a pressure drop in the penetrating liquid and a driving force for the liquid movement by a suggested parabolic penetration model. For cold worked tungsten, a penetration theory was proposed, where an internal stress release in the penetrated tungsten grains creates space for the advancing liquid.

The spreading of the tungsten agglomerates is explained by an interagglomerate melt swelling due to a Kirkendall effect. The liquid matrix undergoes a volume increase since the diffusion rates of Ni-Fe are higher than for W and initial concentration gradients of W and Ni, Fe exists. The suggested model by Kirkendall are also used for an analysis of the interaction behaviour between solid particles and a solidification front and inclusion behaviour in iron base alloys during teeming and deoxidation.

The average tungsten particles size decrease initially since part of the tungsten particles is dissolved when the non-equilibrium matrix phase is melting. When equilibrium is reached, the tungsten particles grow in accordance with the Ostwald ripening process by an approximately 1/3 power law. Larger particle fraction of particles showed a higher growth rate, due to shorter diffusion distances between the particles. Cobalt, Sulphur and absence of iron in the matrix were found to increase the growth rate of the tungsten particles due to a higher surface tension between the solid tungsten particles and the matrix melt.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006.
Series
Trita-MG, ISSN 1104-7127 ; 2006:1
Keyword [en]
Liquid phase sintering, heavy metal, particle composites, tungsten, penetration, agglomerate separation, particle interaction, parabolic flight, sounding rockets, microgravity, Kirkendall effect
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-3870OAI: oai:DiVA.org:kth-3870DiVA: diva2:9818
Public defence
2006-03-22, Sal F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2010-05-28Bibliographically approved
List of papers
1. Liquid Phase Sintering of Tungsten Composites in Space: Results of Tests Performed in Texus
Open this publication in new window or tab >>Liquid Phase Sintering of Tungsten Composites in Space: Results of Tests Performed in Texus
1988 (English)In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 8, no 12, 315-319 p.Article in journal (Refereed) Published
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5441 (URN)10.1016/0273-1177(88)90033-6 (DOI)
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2017-11-21Bibliographically approved
2. Liquid Phase Sintering under Microgravity in Space
Open this publication in new window or tab >>Liquid Phase Sintering under Microgravity in Space
1988 (English)In: Modern developments in powder metallurgy, ISSN 0074-7513, Vol. 18-21, 63- p.Article in journal (Refereed) Published
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5442 (URN)
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2010-05-28Bibliographically approved
3. Liquid-phase Sintering of Tungsten Composites in Space. Agglomerate Separation and Particle Growth
Open this publication in new window or tab >>Liquid-phase Sintering of Tungsten Composites in Space. Agglomerate Separation and Particle Growth
1989 (English)In: High Temperatures-High Pressures, ISSN 0018-1544, E-ISSN 1472-3441, Vol. 21, 507-514 p.Article in journal (Refereed) Published
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5443 (URN)
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2017-11-21Bibliographically approved
4. Microgravity Applications Furnace Facility, MAFF, for Parabolic Flights.
Open this publication in new window or tab >>Microgravity Applications Furnace Facility, MAFF, for Parabolic Flights.
Show others...
1992 (English)In: Proc. VIIIth Europ. Symp. Mat. and Fluid Sci. in Microg, 1992, Vol. 1, 383-386 p.Conference paper, Published paper (Refereed)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5444 (URN)
Conference
VIIIth Europ. Symp. Mat. and Fluid Sci. in Microg
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2010-05-28Bibliographically approved
5. Liquid Phase Sintering of Tungsten Composites under Microgravity: Effect of Matrix Composition. Particle Growth
Open this publication in new window or tab >>Liquid Phase Sintering of Tungsten Composites under Microgravity: Effect of Matrix Composition. Particle Growth
1992 (English)In: Proc. Tungsten & Tungsten Alloys, 97-110 p.Article in journal (Refereed) Published
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5445 (URN)
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2010-05-28Bibliographically approved
6. Liquid Phase Sintering of Tungsten Composites under Microgravity: Effect of Matrix Composition
Open this publication in new window or tab >>Liquid Phase Sintering of Tungsten Composites under Microgravity: Effect of Matrix Composition
1992 (English)In: Microgravity Q., Vol. 2, no 4, 227-232 p.Article in journal (Refereed) Published
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5446 (URN)
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2010-05-28Bibliographically approved
7. Liquid Phase Sintering of Tungsten Composites
Open this publication in new window or tab >>Liquid Phase Sintering of Tungsten Composites
1994 (English)In: Conference proceedings of the Sefström Symposium, Stockholm: KTH , 1994, 293-304 p.Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH, 1994
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5447 (URN)91-7170-789-1 (ISBN)
Conference
The Sefström Symposium in honour of the 175 year anniversary of the School of Metallurgy and Materials Science
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2010-05-28Bibliographically approved
8. Penetration of Tungsten Grain Boundaries by a Liquid Fe-Ni Matrix
Open this publication in new window or tab >>Penetration of Tungsten Grain Boundaries by a Liquid Fe-Ni Matrix
1995 (English)In: International Journal of Refractory Metals and Hard Materials, ISSN 0958-0611, Vol. 13, 173-179 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:kth:diva-5448 (URN)
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2010-05-28Bibliographically approved
9. Liquid Ni-Fe penetration and recrystallisation in tungsten
Open this publication in new window or tab >>Liquid Ni-Fe penetration and recrystallisation in tungsten
2003 (English)In: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 21, no 3-4, 159-170 p.Article in journal (Refereed) Published
Abstract [en]

Melt penetration in grain boundaries of solid tungsten has been investigated. Solid tungsten rods have been exposed to a nickel-iron melt saturated with tungsten and the penetration depth and the shape of the liquid channels have been examined. The solid tungsten samples have been treated in different ways like cold working, annealing and recrystallisation, before melt exposure. Important parameters for the penetration process are stresses, surface tensions, solution and kinetic effects. A new theoretical model for the penetration mechanism in cold worked samples is proposed. Rapid recovery of the grains in the penetrated areas of the cold worked samples was observed. This is discussed, as well.

Keyword
liquid penetration, tungsten, grain boundary, recrystallisation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-5449 (URN)10.1016/S0263-4368(03)00028-3 (DOI)000185117300007 ()
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2017-11-21Bibliographically approved
10. Liquid Penetration and Particle Separation during the Initial Stage of Liquid Phase Sintering
Open this publication in new window or tab >>Liquid Penetration and Particle Separation during the Initial Stage of Liquid Phase Sintering
2006 (English)In: Metallurgical transactions. A, ISSN 0360-2133Article in journal (Refereed) In press
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-5450 (URN)
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2010-05-28Bibliographically approved
11. Interaction behaviour between solid inclusions and solidification front and inclusion behaviour in iron base alloys during teeming and at deoxidation by the Kirkendall Effect
Open this publication in new window or tab >>Interaction behaviour between solid inclusions and solidification front and inclusion behaviour in iron base alloys during teeming and at deoxidation by the Kirkendall Effect
2006 (English)Report (Other academic)
Series
Trita-MG, ISSN 1104-7127
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-5451 (URN)
Note
QC 20100528Available from: 2006-03-08 Created: 2006-03-08 Last updated: 2010-05-28Bibliographically approved

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