A model for stresses, crack generation and fracture toughness calculation in scratched TiN-coated steel surfaces

Kenneth Holmberg (Corresponding Author), Anssi Laukkanen, Helena Ronkainen, Kim Wallin, Simo Varjus

    Research output: Contribution to journalArticleScientificpeer-review

    151 Citations (Scopus)

    Abstract

    The contact situation in a scratch tester, when a spherical rigid diamond tip is sliding with an increasing load over an elastic–plastic steel plate deposited with a 2 μm thick hard ceramic TiN coating is analysed. A three-dimensional finite element model (FEM) for describing the elastic and plastic behaviour and for calculating the stresses and strains has been developed. It shows that the maximum first principal tensile stress is generated in the tail part of the contact area. With increasing load a tetra-armed star shaped stress-field is generated around the contact. After about 1 mm of sliding a peak area of maximum first principal stress is formed in the back-tail region at the border of the scratch groove, creating the first visible angular cracks in the coating. This is in agreement with empirical observations. Once substantial plastic deformation of the substrate has occurred, the maximum tensile stresses are located behind the contact at a distance of 0.5–1 times the contact length from the back edge of the contact. These stresses have a horseshoe shaped ridge of maximum values with an opening in the sliding direction. The change of the state of deformation from sliding over the coating (sliding mode) to deforming the substrate plastically (ploughing mode) characterises the loss of load carrying capacity of the coated surface system. The model is used for calculating the fracture toughness of the coating. The critical fracture toughness is equal to the tensile stress times the square root of half of the crack spacing (Kc=ab/2) when the crack spacing is smaller than the crack length. For determining the fracture toughness of a 2 μm thick TiN coating on steel substrate a suitable crack field turned out to be the transversal tensile cracks in the scratched groove. For the studied case, the fracture toughness of the TiN coating was measured to be Kc=7 MPa m0.5.
    Original languageEnglish
    Pages (from-to)278-291
    Number of pages4
    JournalWear
    Volume254
    Issue number3-4
    DOIs
    Publication statusPublished - 2003
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    Steel
    toughness
    fracture strength
    Fracture toughness
    cracks
    sliding
    steels
    Cracks
    coatings
    Coatings
    tensile stress
    Tensile stress
    grooves
    Substrates
    spacing
    plowing
    Electric load loss
    load carrying capacity
    Hard coatings
    ceramic coatings

    Keywords

    • surface engineering
    • coatings
    • stress modelling
    • fracture
    • scratch test
    • fracture toughness
    • ProperTune

    Cite this

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    title = "A model for stresses, crack generation and fracture toughness calculation in scratched TiN-coated steel surfaces",
    abstract = "The contact situation in a scratch tester, when a spherical rigid diamond tip is sliding with an increasing load over an elastic–plastic steel plate deposited with a 2 μm thick hard ceramic TiN coating is analysed. A three-dimensional finite element model (FEM) for describing the elastic and plastic behaviour and for calculating the stresses and strains has been developed. It shows that the maximum first principal tensile stress is generated in the tail part of the contact area. With increasing load a tetra-armed star shaped stress-field is generated around the contact. After about 1 mm of sliding a peak area of maximum first principal stress is formed in the back-tail region at the border of the scratch groove, creating the first visible angular cracks in the coating. This is in agreement with empirical observations. Once substantial plastic deformation of the substrate has occurred, the maximum tensile stresses are located behind the contact at a distance of 0.5–1 times the contact length from the back edge of the contact. These stresses have a horseshoe shaped ridge of maximum values with an opening in the sliding direction. The change of the state of deformation from sliding over the coating (sliding mode) to deforming the substrate plastically (ploughing mode) characterises the loss of load carrying capacity of the coated surface system. The model is used for calculating the fracture toughness of the coating. The critical fracture toughness is equal to the tensile stress times the square root of half of the crack spacing (Kc=ab/2) when the crack spacing is smaller than the crack length. For determining the fracture toughness of a 2 μm thick TiN coating on steel substrate a suitable crack field turned out to be the transversal tensile cracks in the scratched groove. For the studied case, the fracture toughness of the TiN coating was measured to be Kc=7 MPa m0.5.",
    keywords = "surface engineering, coatings, stress modelling, fracture, scratch test, fracture toughness, ProperTune",
    author = "Kenneth Holmberg and Anssi Laukkanen and Helena Ronkainen and Kim Wallin and Simo Varjus",
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    language = "English",
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    A model for stresses, crack generation and fracture toughness calculation in scratched TiN-coated steel surfaces. / Holmberg, Kenneth (Corresponding Author); Laukkanen, Anssi; Ronkainen, Helena; Wallin, Kim; Varjus, Simo.

    In: Wear, Vol. 254, No. 3-4, 2003, p. 278-291.

    Research output: Contribution to journalArticleScientificpeer-review

    TY - JOUR

    T1 - A model for stresses, crack generation and fracture toughness calculation in scratched TiN-coated steel surfaces

    AU - Holmberg, Kenneth

    AU - Laukkanen, Anssi

    AU - Ronkainen, Helena

    AU - Wallin, Kim

    AU - Varjus, Simo

    PY - 2003

    Y1 - 2003

    N2 - The contact situation in a scratch tester, when a spherical rigid diamond tip is sliding with an increasing load over an elastic–plastic steel plate deposited with a 2 μm thick hard ceramic TiN coating is analysed. A three-dimensional finite element model (FEM) for describing the elastic and plastic behaviour and for calculating the stresses and strains has been developed. It shows that the maximum first principal tensile stress is generated in the tail part of the contact area. With increasing load a tetra-armed star shaped stress-field is generated around the contact. After about 1 mm of sliding a peak area of maximum first principal stress is formed in the back-tail region at the border of the scratch groove, creating the first visible angular cracks in the coating. This is in agreement with empirical observations. Once substantial plastic deformation of the substrate has occurred, the maximum tensile stresses are located behind the contact at a distance of 0.5–1 times the contact length from the back edge of the contact. These stresses have a horseshoe shaped ridge of maximum values with an opening in the sliding direction. The change of the state of deformation from sliding over the coating (sliding mode) to deforming the substrate plastically (ploughing mode) characterises the loss of load carrying capacity of the coated surface system. The model is used for calculating the fracture toughness of the coating. The critical fracture toughness is equal to the tensile stress times the square root of half of the crack spacing (Kc=ab/2) when the crack spacing is smaller than the crack length. For determining the fracture toughness of a 2 μm thick TiN coating on steel substrate a suitable crack field turned out to be the transversal tensile cracks in the scratched groove. For the studied case, the fracture toughness of the TiN coating was measured to be Kc=7 MPa m0.5.

    AB - The contact situation in a scratch tester, when a spherical rigid diamond tip is sliding with an increasing load over an elastic–plastic steel plate deposited with a 2 μm thick hard ceramic TiN coating is analysed. A three-dimensional finite element model (FEM) for describing the elastic and plastic behaviour and for calculating the stresses and strains has been developed. It shows that the maximum first principal tensile stress is generated in the tail part of the contact area. With increasing load a tetra-armed star shaped stress-field is generated around the contact. After about 1 mm of sliding a peak area of maximum first principal stress is formed in the back-tail region at the border of the scratch groove, creating the first visible angular cracks in the coating. This is in agreement with empirical observations. Once substantial plastic deformation of the substrate has occurred, the maximum tensile stresses are located behind the contact at a distance of 0.5–1 times the contact length from the back edge of the contact. These stresses have a horseshoe shaped ridge of maximum values with an opening in the sliding direction. The change of the state of deformation from sliding over the coating (sliding mode) to deforming the substrate plastically (ploughing mode) characterises the loss of load carrying capacity of the coated surface system. The model is used for calculating the fracture toughness of the coating. The critical fracture toughness is equal to the tensile stress times the square root of half of the crack spacing (Kc=ab/2) when the crack spacing is smaller than the crack length. For determining the fracture toughness of a 2 μm thick TiN coating on steel substrate a suitable crack field turned out to be the transversal tensile cracks in the scratched groove. For the studied case, the fracture toughness of the TiN coating was measured to be Kc=7 MPa m0.5.

    KW - surface engineering

    KW - coatings

    KW - stress modelling

    KW - fracture

    KW - scratch test

    KW - fracture toughness

    KW - ProperTune

    U2 - 10.1016/S0043-1648(02)00297-1

    DO - 10.1016/S0043-1648(02)00297-1

    M3 - Article

    VL - 254

    SP - 278

    EP - 291

    JO - Wear

    JF - Wear

    SN - 0043-1648

    IS - 3-4

    ER -