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The early stage of galling
Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.ORCID iD: 0000-0002-8144-8821
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2012. , 41 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2012:51
Keyword [en]
Galling, Stainless steel, Tool steel, Friction, Sliding wear, SOFS, Tribology, Wear
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
URN: urn:nbn:se:kau:diva-15345ISBN: 978-91-7063-462-8 (print)OAI: oai:DiVA.org:kau-15345DiVA: diva2:563348
Presentation
2012-12-07, Eva Erikssonsalen, 21A 342, Karlstads Universitet, Karlstad, 13:15 (English)
Opponent
Supervisors
Available from: 2012-11-21 Created: 2012-10-26 Last updated: 2017-12-06Bibliographically approved
List of papers
1. Galling resistance and wear mechanisms for cold-work tool steels in lubricated sliding against high strength stainless steel sheets
Open this publication in new window or tab >>Galling resistance and wear mechanisms for cold-work tool steels in lubricated sliding against high strength stainless steel sheets
2012 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 286-287, 92-97 p.Article in journal (Refereed) Published
Abstract [en]

Tool damage in sheet metal forming of stainless steel is of high concern for the forming industry. In the present work, ingot cast AISI D2 and advanced powder metallurgy tool steel (PM) cold-work tool steels were evaluated and ranked regarding wear mechanisms and galling resistance. Wear tests were performed using a slider-on-flat-surface (SOFS) tribometer in sliding against austenitic–ferritic (duplex) stainless steel sheets at different contact pressures in lubricated conditions. The best galling resistance was observed for the nitrogen alloyed PM tool steels. Abrasive scratching of the tool surfaces and transfer of sheet material due to adhesive wear were the main metal forming tool surface damage mechanisms. By increasing the hardness of one PM sheet metal forming tool grade, the galling resistance was enhanced.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2012
Keyword
Galling, Wear, Tribology, Stainless steel, Tool steel
National Category
Tribology
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-15337 (URN)10.1016/j.wear.2011.04.002 (DOI)000304743600012 ()
Note

Tribology in Manufacturing Processes

Available from: 2012-10-26 Created: 2012-10-26 Last updated: 2017-12-07Bibliographically approved
2. Galling resistance evaluation of tool steels by two different laboratory test methods for sheet metal forming
Open this publication in new window or tab >>Galling resistance evaluation of tool steels by two different laboratory test methods for sheet metal forming
Show others...
2012 (English)In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 24, no 6, 263-272 p.Article in journal (Refereed) Published
Abstract [en]

Adhesive accumulation of work material on the tool surface is today a major problem in many sheet metal-forming applications. Different laboratory test methods are used to investigate galling with respect to different tool materials, lubricants and process conditions. In the present study, the galling resistance of a modern nitrogen-alloyed powder metallurgy tool steel and an conventional ingot cast D2 type tool steel was evaluated under lubricated sliding against ferritic stainless steel sheets using a commercial pin-on-disc (POD) and an in-house made slider-on-flat-surface (SOFS) tribotester. The investigated tool steels ranked similarly in terms of galling resistanc in both test methods. However, sliding distances to galling were longer for the SOFS equipment due to continuous sliding on new lubricated sheet surface. Best performance was demonstrated by the powder metallurgy tool steel treated to 65 HRC. Differences in friction behaviour and galling initiation were analysed on the basis of the two different working conditions, i.e. open (SOFS) and closed (POD) tribosystems. Copyright © 2012 John Wiley & Sons, Ltd.

Place, publisher, year, edition, pages
John Wiley & Sons, 2012
Keyword
slider-on-flat-surface, pin-on-disc, sheet metal forming, galling, stainless steel
National Category
Tribology
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-15338 (URN)10.1002/ls.1180 (DOI)000308637600002 ()
Available from: 2012-10-26 Created: 2012-10-26 Last updated: 2017-12-07Bibliographically approved
3. Influence of work material proof stress and tool steel microstructure on galling initiation and critical contact pressure
Open this publication in new window or tab >>Influence of work material proof stress and tool steel microstructure on galling initiation and critical contact pressure
2013 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 60, 104-110 p.Article in journal (Refereed) Published
Abstract [en]

EN 1.4301 (austenitic), EN 1.4509 (ferritic), EN 1.4162 (duplex) and EN 1.4310 C1000 (metastable austenitic) stainless steels were tested in lubricated sliding against an ingot cast EN X153WCrMoV12 and powder metallurgy nitrogen alloyed Uddeholm Vancron 40 tool steels to reveal critical to galling contact pressure, Pcr. The calculated Pcr were higher for steels with higher strength. At P>Pcr, due to plastic flow of sheet material, the tool is damaged substantially and wear-induced matrix damage causes rapid galling initiation. At P<Pcr, galling was not observed. The powder metallurgy tool steel was more resistant to galling against all tested stainless steels. Better performance was associated with fine and homogeneously distributed hard phases preventing intensive wear of the tool steel matrix.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2013
Keyword
Galling, Tool steels, Stainless steel, Wear
National Category
Tribology
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-15340 (URN)10.1016/j.triboint.2012.10.023 (DOI)000315550700014 ()
Note

The article had the status accepted at the time of P. Karlssons licentiate defense.

Available from: 2012-10-26 Created: 2012-10-26 Last updated: 2017-12-07Bibliographically approved
4. Influence of size and distribution of hard phases in tool steels on the early stage of galling
Open this publication in new window or tab >>Influence of size and distribution of hard phases in tool steels on the early stage of galling
2012 (English)In: / [ed] Harald Leitner, Regina Kranz, Angelica Tremmel, 2012, 469-476 p.Conference paper, Published paper (Refereed)
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.

Keyword
Galling, Stainless steel, Tool steel, SOFS
National Category
Tribology
Identifiers
urn:nbn:se:kau:diva-15339 (URN)978-3-901384-52-3 (ISBN)
Conference
9th International tooling conference, 11-14 September 2012, Montanuniversität Leoben, Austria
Available from: 2012-10-26 Created: 2012-10-26 Last updated: 2017-12-06Bibliographically approved

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