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Influence of size and distribution of hard phases in tool steels on the early stage of galling
Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik. (Materialteknik)ORCID-id: 0000-0002-8144-8821
Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik. (Materialvetenskap)
Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik. (Materialvetenskap)ORCID-id: 0000-0002-9441-2502
Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik. (Materialvetenskap)ORCID-id: 0000-0001-6029-2613
2012 (engelsk)Inngår i: / [ed] Harald Leitner, Regina Kranz, Angelica Tremmel, 2012, s. 469-476Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

In sheet metal forming processes, contact pressures are relatively high and total sliding distances are long, which demands tool steels to prevent tool damage and to resist galling. Galling is related to microscopic and macroscopic material transfer, but, the mechanisms of initiation are not thoroughly understood.

 

To investigate galling initiation, lubricated sliding testing in the Slider-On-Flat-Surface (SOFS) tribometer was performed for ingot cast (IC) AISI D2 type and nitrogen alloyed powder metallurgy (PM) tool steel. The sheet grade was EN 1.4509 ferritic stainless steel. To reveal mechanisms in the early stages of galling initiation, transfer and accumulation of sheet material to the tool surfaces were characterized using AFM and SEM.

 

It was found that already after a short sliding distance, transfer of sheet material occurred covering both the matrix and the hard phases. Macroscopic analysis of the contact area showed that initial material transfer and further lump growth occurred at positions corresponding to high plastic strains in the sheet material. Even though initial material transfer was observed for both tested tool steels, the sliding distance to the point where transfer and further lump formation occurred was longer for the PM tool steel. This was discussed in correlation to differences in size and distribution of the hard phases in the tool steels, which was confirmed by AFM and SEM.

sted, utgiver, år, opplag, sider
2012. s. 469-476
Emneord [en]
Galling, Stainless steel, Tool steel, SOFS
HSV kategori
Identifikatorer
URN: urn:nbn:se:kau:diva-15339ISBN: 978-3-901384-52-3 (tryckt)OAI: oai:DiVA.org:kau-15339DiVA, id: diva2:562946
Konferanse
9th International tooling conference, 11-14 September 2012, Montanuniversität Leoben, Austria
Tilgjengelig fra: 2012-10-26 Laget: 2012-10-26 Sist oppdatert: 2020-01-29bibliografisk kontrollert
Inngår i avhandling
1. The early stage of galling
Åpne denne publikasjonen i ny fane eller vindu >>The early stage of galling
2012 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

In sheet metal forming (SMF) of materials such as stainless steels there is a major problem with transfer and accumulation of sheet material to the metal forming tool surface. The problem is known as galling; a kind of severe adhesive wear, which results in severe scratching of produced parts. In this thesis, galling observed in contacts between tool steels and stainless steel sheets under lubricated sliding conditions was studied, focusing on the early stage of galling. It was found that changes in friction cannot be used as galling indicator in the early stage of galling because transfer and accumulation of sheet material happens even though friction is low and stable. The progression of galling is influenced by tool steel damage occurring around the tool steel hard phases caused by sheet material flow, which results in formation of wear-induced galling initiation sites. A correlation between the critical contact pressure to galling and sheet material proof stress was found. Galling happened at lower pressures for sheet material with lower proof stress possibly due to easier sheet material flow, resulting in quicker tool damage. Material transfer and tool steel damage were delayed for tool steels comprising homogenously distributed, small and high hard phases. Additionally, the galling resistance was higher for tool steels with higher hardness due to decreased tool steel damage. In a comparison between observations of the worn tool surfaces after wear tests and calculations in FEM it was found that material transfer did not take place at regions with highest contact pressures but at regions with highest plastic strains. The results obtained in this thesis indicate that tool steel damage and sheet material flow occurring in the contact during sliding are important factors influencing galling.

sted, utgiver, år, opplag, sider
Karlstad: Karlstads universitet, 2012. s. 41
Serie
Karlstad University Studies, ISSN 1403-8099 ; 2012:51
Emneord
Galling, Stainless steel, Tool steel, Friction, Sliding wear, SOFS, Tribology, Wear
HSV kategori
Forskningsprogram
Materialteknik
Identifikatorer
urn:nbn:se:kau:diva-15345 (URN)978-91-7063-462-8 (ISBN)
Presentation
2012-12-07, Eva Erikssonsalen, 21A 342, Karlstads Universitet, Karlstad, 13:15 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2012-11-21 Laget: 2012-10-26 Sist oppdatert: 2020-01-29bibliografisk kontrollert
2. The influence of tool steel microstructure on galling
Åpne denne publikasjonen i ny fane eller vindu >>The influence of tool steel microstructure on galling
2014 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

In sheet metal forming (SMF) of materials such as stainless steels there is a major problem with transfer and accumulation of sheet material to the metal forming tool surface. The problem is known as galling; a sort of severe adhesive wear, which results in severe scratching of produced parts. In this thesis, the overall aim was to gain knowledge of the influence of tool steel microstructure on galling initiation under sliding conditions. It was discovered that material transfer and tool steel damage caused by sheet material flow creating wear-induced galling initiation sites occurred in the early stage of galling. The galling resistance was higher for tool steels with higher matrix hardness due to better resistance to tool steel damage. Initial friction and critical contact pressure to galling was influenced by the strength of the sheet material. Material transfer happened at low pressures and the friction value was high in a case of sheet materials with lower proof strength, possibly due to the sheet contact against the tool steel matrix resulting in high adhesion and quicker tool damage. It was demonstrated that, in addition to hardness of the tool steel matrix and sheet material proof strength, tool steel microstructural features like size, shape, distribution and height of hard phases are important parameters influencing galling. Tool steels comprising homogeneously distributed, small and high hard phases better prevented the contact between sheet material and the tool steel matrix. Thus, a metal to metal contact with high friction was more efficiently avoided, which resulted in better tool performance.

 

sted, utgiver, år, opplag, sider
Karlstad: Karlstads universitet, 2014. s. 42
Serie
Karlstad University Studies, ISSN 1403-8099 ; 2014:35
Emneord
Galling, Microstructure, Material transfer, Tool steel, Stainless steel, Metall transfer
HSV kategori
Forskningsprogram
Materialteknik
Identifikatorer
urn:nbn:se:kau:diva-32113 (URN)978-91-7063-568-7 (ISBN)
Disputas
2014-08-29, Ljungbergsalen, 21A 244, Universitetsgatan 2, Karlstad, 10:15 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2014-06-17 Laget: 2014-05-19 Sist oppdatert: 2020-01-29bibliografisk kontrollert

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