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Research Papers: Friction and Wear

Tribological Behavior of Tool Steel Under Press Hardening Conditions Using Simulative Tests

[+] Author and Article Information
Sergej Mozgovoy

Division of Machine Elements,
Luleå University of Technology,
Luleå 97187, Sweden
e-mail: sergej.mozgovoy@ltu.se

Jens Hardell

Division of Machine Elements,
Luleå University of Technology,
Luleå 97187, Sweden
e-mail: jens.hardell@ltu.se

Liang Deng

Division of Mechanics of Solid Materials,
Luleå University of Technology,
Luleå 97187, Sweden
e-mail: liang.deng@ltu.se

Mats Oldenburg

Professor
Division of Mechanics of Solid Materials,
Luleå University of Technology,
Luleå 97187, Sweden
e-mail: mats.oldenburg@ltu.se

Braham Prakash

Professor
Division of Machine Elements,
Luleå University of Technology,
Luleå 97187, Sweden
e-mail: braham.prakash@ltu.se

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received March 22, 2017; final manuscript received May 17, 2017; published online August 2, 2017. Assoc. Editor: Stephen Boedo.

J. Tribol 140(1), 011606 (Aug 02, 2017) (11 pages) Paper No: TRIB-17-1105; doi: 10.1115/1.4036924 History: Received March 22, 2017; Revised May 17, 2017

Press hardening is employed in the automotive industry to produce advanced high-strength steel components for safety and structural applications. This hot forming process depends on friction as it controls the deformation of the sheet. However, friction is also associated with wear of the forming tools. Tool wear is a critical issue when it comes to the dimensional accuracy of the produced components and it reduces the service life of the tool. It is therefore desirable to enhance the durability of the tools by studying the influence of high contact pressures, cyclic thermal loading, and repetitive mechanical loading on tool wear. This is difficult to achieve in conventional tribological testing devices. Therefore, the tribological behavior of tool–workpiece material pairs at elevated temperatures was studied in a newly developed experimental setup simulating the conditions prevalent during interaction of the hot sheet with the tool surface. Uncoated 22MnB5 steel and aluminum–silicon (Al–Si)-coated 22MnB5 steel were tested at 750 °C and 920 °C, respectively. It was found that higher loads led to lower and more stable friction coefficients independent of sliding velocity or surface material. The influence of sliding velocity on the coefficient of friction was only marginal. In the case of Al–Si-coated 22MnB5, the friction coefficient was generally higher and unstable due to transfer of Al–Si coating material to the tool. Adhesion was the main wear mechanism in the case of uncoated 22MnB5.

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References

Figures

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Fig. 1

Main features of simulative testing device

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Fig. 2

Schematic showing test configuration employed in tribological studies; FN is the normal force, FF is the friction force, FP is the pretension force, T is the temperature of the sheet, and s is the sliding distance per sheet strip

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Fig. 3

Mean coefficient of friction as a function of sliding velocity for (a) 50 N normal load and (b) 150 N normal load

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Fig. 4

Mean coefficient of friction as a function of normal load for (a) 0.01 m s−1 sliding velocity and (b) 0.1 m s−1 sliding velocity

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Fig. 5

Coefficient of friction as a function of sheet strip position for the fifth (a) uncoated 22MnB5 steel strip and (b) Al–Si-coated 22MnB5 steel strip

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Fig. 6

Mean coefficient of friction as a function of number of tested strips for (a) uncoated 22MnB5 steel and (b) Al–Si-coated 22MnB5 steel

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Fig. 7

Mean wear coefficient as a function of sliding velocity for (a) 50 N normal load and (b) 150 N normal load

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Fig. 8

Mean wear coefficient as a function of normal load for (a) 0.01 m s−1 sliding velocity and (b) 0.1 m s−1 sliding velocity

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Fig. 10

Scanning electron micrographs in backscatter electron mode of stationary tool steel specimens tested at (a) 150 N and 0.01 m s−1 and (b) 150 N and 0.1 m s−1 and movable tool steel specimens tested at (c) 150 N and 0.01 m s−1 and (d) 150 N and 0.1 m s−1 against uncoated 22MnB5; arrows indicate the sliding direction

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Fig. 11

EDS spectra taken in (a) point 1 and (b) point 2 as indicated in Fig. 9(c) on a tool steel specimen that was tested at 50 N normal load and 0.01 m s−1 sliding velocity against uncoated 22MnB5 steel

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Fig. 9

Scanning electron micrographs in backscatter electron mode of stationary tool steel specimens tested at (a) 50 N and 0.01 m s−1 and (b) 50 N and 0.1 m s−1 and movable tool steel specimens tested at (c) 50 N and 0.01 m s−1 and (d) 50 N and 0.1 m s−1 against uncoated 22MnB5; arrows indicate the sliding direction

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Fig. 12

Scanning electron micrographs in backscatter electron mode of stationary tool steel specimens tested at (a) 50 N and 0.01 m s−1 and (b) 50 N and 0.1 m s−1 and movable tool steel specimens tested at (c) 50 N and 0.01 m s−1 and (d) 50 N and 0.1 m s−1 against Al–Si-coated 22MnB5; arrows indicate the sliding direction

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Fig. 13

Scanning electron micrographs in backscatter electron mode of stationary tool steel specimens tested at (a) 150 N and 0.01 m s−1 and (b) 150 N and 0.1 m s−1 and movable tool steel specimens tested at (c) 150 N and 0.01 m s−1 and (d) 150 N and 0.1 m s−1 against Al–Si-coated 22MnB5; arrows indicate the sliding direction

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Fig. 14

EDS spectra taken in (a) point 1 and (b) point 2 as indicated in Fig. 13(c) on a tool steel specimen that was tested at 150 N normal load and 0.01 m s−1 sliding velocity against Al–Si-coated 22MnB5 steel

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Fig. 15

Scanning electron micrographs in secondary electron mode of (a) worn Al–Si-coated 22MnB5 steel tested at 50 N load and 0.1 m s−1 sliding velocity and (b) worn uncoated 22MnB5 steel tested at 150 N load and 0.01 m s−1 sliding velocity; arrows indicate the sliding direction

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