Investigation of the stresses and stress intensity factors responsible for fracture of thin protective films during ultra-micro indentation tests with spherical indenters

Weppelmann, E.R.; Swain, Michael V.

doi:10.1016/s0040-6090(95)08525-4

Cited by 105 publications

(42 citation statements)

References 11 publications

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“…Thin films (Fig. 2c): Cracking becomes suppressed within the compression zone beneath the Hertzian contact, and the maximum tensile stresses shift back to the top surface close to the contact circle [39][40][41]. Membrane stresses come increasingly into play.…”

Section: Theoretical Aspects In Single Vs Multilayer Deformation -Fementioning

confidence: 99%

Microscale interpretation of tribological phenomena in Ti/TiN soft-hard multilayer coatings on soft austenite steel substrates

Lackner¹,

Major²,

Kot³

2011

Bulletin of the Polish Academy of Sciences: Technical Sciences

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Abstract. The mechanical and tribological behavior of physical vapor deposited coatings on soft substrate materials gains increasing interest due to economical and environmental aspects -e.g. substitution of steels by light-weight metals or polymers in transport vehicles. Nevertheless, such soft materials require surface protection against wear in tribological contacts. Single layer hard coatings deposited at room temperature are brittle with a relatively poor adhesion. Therefore, they should be better substituted by tough multilayer coatings of soft-hard material combinations. However, the mechanics of such multilayer coatings with several 10 nm thick bilayer periods is difficult and yet not well described. The presented work tries to fill the gap of knowledge by focusing both on mechanical investigations of hardness, adhesion, and wear and on microscopic elucidation of deformation mechanisms. In the paper 1 µm thick Ti/TiN multilayer stacks were deposited by magnetron sputtering on soft austenitic steel substrates at room temperature to prevent distortion of functional components in future applications. High hardness was found for 8 and 16 bilayer films with modulation ratio Ti:TiN = 1:2 and 1:4. This was attributed (with use of transmission electron microscopy) to stopping the crack propagation in thin Ti layers of the multilayer systems by shear deformation combined with different fracture mechanisms in comparison with that for the TiN single layers (edge cracks at the border of the contact area and ring cracks outside, respectively).

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Section: Theoretical Aspects In Single Vs Multilayer Deformation -Fementioning

confidence: 99%

Microscale interpretation of tribological phenomena in Ti/TiN soft-hard multilayer coatings on soft austenite steel substrates

Lackner¹,

Major²,

Kot³

2011

Bulletin of the Polish Academy of Sciences: Technical Sciences

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“…These observations were thus related to dislocation motion in general, and in particular to dislocation nucleation [3][4][5][6][7] or to dislocation source activation. [8,9] One of the major challenges in assessing the behavior of the elastic-plastic transition during nanoindentation is the difficulty in ascribing the behavior to homogeneous dislocation nucleation, [10] the activation of well-spaced dislocation sources, the activation of a point defect source (i.e., a vacancy), [9] and the tensile fracture of a surface film, [11][12][13][14] or some other surface film relationship with the underlying dislocation structure. [15] For instance, in a well-annealed metallic single crystal, it is not unreasonable to assume a dislocation density on the order of 10 11 m -2 .…”

Section: Introductionmentioning

confidence: 99%

Dislocation Nucleation and Source Activation during Nanoindentation Yield Points

Zbib

Bahr

2007

Metall Mater Trans A

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The onset of plasticity during nanoindentation of a tungsten single crystal was examined as a function of pre-existing dislocation density. Vickers indentations were used to generate a spatially varying dislocation density, and nanoindentation was then carried out at regions of high and low dislocation densities. Even with dislocation densities as high as 1.8 · 10 13 m -2 , a sharp elastic-plastic transition was observed during some indentations. At lower dislocation densities, 3.5 · 10 9 m -2 , the shear stress at the elastic plastic transition increased and approached the theoretical shear stress of the crystal. A first-order model that predicts the load required for the onset of plasticity during nanoindentation from the activation of a dislocation source within a critical volume of material, rather than homogeneous dislocation nucleation, is developed. The model correlates well with experimentally measured loads at the onset of plasticity for dislocation densities of 10 12 m -2 and higher for these nanoindentation conditions.

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“…It was shown that film failure was caused by large tensile stresses in the surface region outside the contact radius . [12] The large tensile stress at the surface for thin films was proven by Chai and Lawn using finite element analysis . [13] The representative curves for mode I stress intensity factor against a/hf showed the same trends as the current study .…”

Section: Mtot = Mb -Msubmentioning

confidence: 98%

“…The radial stress has been demonstrated to cause the through thickness cracking of a hard film on soft substrate . [12] The radial stress prior to fracture can be estimated from a superposition of the bending stress and stretching stress created from the contact load [48] …”

Section: -40 50mentioning

confidence: 99%

Development of experimental verification techniques for non-linear deformation and fracture on the nanometer scale.

Moody¹,

Bahr²

2005

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This work covers three distinct aspects of deformation and fracture during indentations. In particular, we develop an approach to verification of nanoindentation induced film fracture in hard film / soft substrate systems ; we examine the ability to perform these experiments in harsh environments; we investigate the methods by which the resulting deformation from indentation can be quantified and correlated to computational simulations, and we examine the onset of plasticity during indentation testing.First, nanoindentation was utilized to induce fracture of brittle thin oxide films on compliant substrates . During the indentation, a load is applied and the penetration depth is continuously measured . A sudden discontinuity, indicative of film fracture, was observed upon the loading portion of the load-depth curve . The mechanical properties of thermally grown oxide films on various substrates were calculated using two different numerical methods . The first method utilized a plate bending approach by modeling the thin film as an axisymmetric circular plate on a compliant foundation . The second method measured the applied energy for fracture. The crack extension force and applied stress intensity at fracture was then determined from the energy measurements.Secondly, slip steps form on the free surface around indentations in most crystalline materials when dislocations reach the free surface . Analysis of these slip steps provides information about the deformation taking place in the material . Techniques have now been developed to allow for accurate and consistent measurement of slip steps and the effects of crystal orientation and tip geometry are characterized . These techniques will be described and compared to results from dislocation dynamics simulations.iii Finally, the stress required to cause fracture of passive films on stainless steels was studied using nanoindentation under in situ and ex situ conditions . For films formed at a passive potential, the alloy chemistry dominated the film strength . Increasing the electrolyte salt concentration from O .O1M NaCl to O .1M NaCl and changing the substrate on which the film was grown from 904L to 304 stainless steels reduced the applied tensile stress for fracture from 1 .74GPa to 1 .63GPa and from 1 .76GPa to 1 .63GPa, respectively . Trends in film strength as a function of environment are the same between in situ and ex situ testing, suggesting the two tests are both feasible methods of analyzing environmental effects on film strength.iv CONTENTS

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Investigation of the stresses and stress intensity factors responsible for fracture of thin protective films during ultra-micro indentation tests with spherical indenters

Cited by 105 publications

References 11 publications

Microscale interpretation of tribological phenomena in Ti/TiN soft-hard multilayer coatings on soft austenite steel substrates

Microscale interpretation of tribological phenomena in Ti/TiN soft-hard multilayer coatings on soft austenite steel substrates

Dislocation Nucleation and Source Activation during Nanoindentation Yield Points

Development of experimental verification techniques for non-linear deformation and fracture on the nanometer scale.

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