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

@article{81724062a2d04ed5882d54fea519376e,
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",
year = "2003",
doi = "10.1016/S0043-1648(02)00297-1",
language = "English",
volume = "254",
pages = "278--291",
journal = "Wear",
issn = "0043-1648",
publisher = "Elsevier",
number = "3-4",

}

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 -