Surface stresses in coated steel surfaces: Influence of a bond layer on surface fracture

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

    Research output: Contribution to journalArticleScientificpeer-review

    23 Citations (Scopus)

    Abstract

    Thin hard coatings in the thickness range of only a few micrometers deposited by physical vapour deposition (PVD) on components or tools can improve the friction and wear properties by several orders of magnitude. A 2 μm thick TiN (E=300 GPa) coating on a high-speed steel substrate with a bond layer at the interface between the coating and the substrate was modelled by micro-level three-dimensional finite-element method (3D FEM) in order to optimise a coated surface with regard to coating fracture. Both compliant low modulus (E=100 GPa) and stiff high modulus (E=500 GPa) bond layers at the coating/substrate interface of 200 and 500 nm thickness were investigated. First principal stresses were simulated for scratch test geometry in the load range of 7.5–15 N. Very high stress concentrations of above 5700 MPa tensile stresses were observed in the bond layer just behind the contact zone for the stiffer bond layer. The stiff bond layer generated 5 times higher tensile stress maxima compared to the compliant bond layer. There was approximately 3.5 times larger strain in the compliant bond layer compared to the stiff bond layer. The general coating design advice based on this exercise is that when a bond layer is used e.g. for coating/substrate adhesion improvement should the bond layer be less stiff than the coating not to generate high and critical tensile stresses. The thickness of the bond layer may vary and is not critical with respect to generated stresses in the surface.
    Original languageEnglish
    Pages (from-to)137-148
    Number of pages12
    JournalTribology International
    Volume42
    Issue number1
    DOIs
    Publication statusPublished - 2009
    MoE publication typeA1 Journal article-refereed
    Event34th Leeds-Lyon Symposium on Tribology - Lyon, France
    Duration: 4 Sep 20077 Sep 2007

    Keywords

    • Hard coating
    • Finite-element method model
    • Coating adhesion
    • ProperTune

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