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Study of the interface between adhered sheet metaland tool steel subjected to adhesive wear
Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.ORCID iD: 0000-0002-1225-0598
Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
Uppsala Universitet. (Ångströmslaboratoriet)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Many products used every day have at least some parts manufactured by sheet metal forming.Sheet metal forming is well suited for mass production and many machines perform aforming step in a matter of seconds. A common and severe form of wear is called gallingand occurs as small amounts of the sheet material is transferred on to the tool.In the present study the interface between three different sheet materials and a powdermetallurgical tool steel was investigated based on morphology and chemical composition.The sheets used were a high strength carbon steel sheet CS, a stainless steel grade, SS andtitanium, Ti. The tool steel, Vancron 40, was selected based on previously shown resistanceto galling. The microstructure of the tool steel contains three major constituents, the steelmatrix, M6C carbides and MCN carbonitrides, each constituent with potentially differentadhesive properties.To investigate the interfaces between the tool and the adhered material cross sectionlamellas was cut using a focused ion beam and studied in a transmission electron microscope.The chemical compositions of the interfaces were also investigated using electronenergy-loss spectroscopyThe presence of an interlayer between the tool and the adhered material would be ofhigh interest as the adhesion in the interface governs galling. The study did not reveal anyinterlayer between tool constituents and adhered material, for Vancron 40 worn against CSand SS but for one combination. SS sheet showed a ≃ 10 nm morphological interlayeragainst a MCN carbonitride. The lubricant was removed from the contact area and no traceof it was left in the interface between tool and adhered sheet. This shows that adhesive wearoccurs during direct tool to sheet contact comparative to dry sliding in SOFS tests.

Keyword [en]
Galling, Interface, Micro structure
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
URN: urn:nbn:se:kau:diva-31842OAI: oai:DiVA.org:kau-31842DiVA: diva2:710019
Available from: 2014-04-04 Created: 2014-04-04 Last updated: 2014-11-19Bibliographically approved
In thesis
1. Adhesive wear testing and modelling of tool steels sliding against sheet metals
Open this publication in new window or tab >>Adhesive wear testing and modelling of tool steels sliding against sheet metals
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sheet metal forming is a manufacturing method used because of its versatility. Sheets are plastically deformed by a tool to create a product. A tool is expected to last for several 100,000 forming operations and efforts are made to optimize the tools. A common type of wear referred to as galling is the adhesion of sheet material to the tools. This problem has become more prevalent as new high strength sheet materials have been developed at the same time as lubricants have become heavily regulated. This has forced the development of new tool steels with improved resistance to galling. There are many parameters influencing the response to galling. In this work the influence of surface preparation, contact geometry, material selection and lubrication has been investigated. The surface of the forming tools has a large influence on the tools effective life. To refurbish a forming tool is expensive and often requires special shops and hand polishing. The influence on galling of different surface preparations suited for sheet metal forming was investigated using a strip-reduction equipment. The contact conditions of a tool sliding against metal sheets were investigated using FE models. The contact conditions were calculated for a U-bending test and for a sliding-on-flat-surface wear tester. The results were compared to those found in literature. One model incorporated the surface roughness of a sheet as measured by optical profilometry. The strength of the interface between the tool and the sheet material determine if material can be transferred onto the tool. The interface between the tool and adhered sheet material was closely studied using transmission electron microscopy of thin lamellas produced by focused ion beam milling. This showed sheet material adhering to the tool without the formation of an interlayer. Finally, several different combinations of tool steels and sheet materials were tested with regards to their ability to withstand galling.

Abstract [en]

Baksidestext:

Sheet metal forming can be used to produce a wide range of products but the initial costs are high as the forming tools are expensive. Wear of the tools in the form of galling i.e. the adhesion of tiny pieces of sheet material to the tools has become more prevalent as high strength sheet materials have been developed and lubricants have become heavily regulated.

In this work the influence on galling of surface preparation, contact geometry, material selection and lubrication has been investigated. It was found that tool surfaces should be polished as rougher surfaces quickly picked up material that adhered to the tools and subsequently scratched the sheets. The strength of the interface between the tool and the sheet material determine if material can be transferred onto the tool. The interface was studied using bright field transmission electron microscopy and the sheet material was found to adhere to the tool without the formation of an interlayer. The conditions under which galling occurs were studied using a slider on flat surface wear tester and several different material combinations were tested with regards to their galling resistance. The contact conditions of the test equipment were also modeled using FE models to better understand the strains of the materials involved.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2014. 64 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2014:25
Keyword
Adhesive wear
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-31793 (URN)978-91-7063-556-4 (ISBN)
Public defence
2014-05-09, 21A342, Eva Erikssonsalen, Karlstad, 10:15 (English)
Opponent
Supervisors
Available from: 2014-05-05 Created: 2014-03-30 Last updated: 2014-05-05Bibliographically approved

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