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The role of α″ orthorhombic phase content on the tenacity and fracture toughness behavior of Ti-22Nb-10Zr coating used in the design of long-term medical implants

The role of α″ orthorhombic phase content on the tenacity and fracture toughness behavior of Ti-22Nb-10Zr coating used in the design of long-term medical implants
The role of α″ orthorhombic phase content on the tenacity and fracture toughness behavior of Ti-22Nb-10Zr coating used in the design of long-term medical implants

Tenacity and fracture toughness of a novel β/α″ Ti-22Nb-10Zr (wt.%) coating processed by magnetron sputtering were modified as a result of the martensitic transformation (β → α″) activated by the presence of compressive residual stresses when the coating deposition is performed at high bias voltage values. Mechanical properties, such as hardness, H, and Young's modulus, E, values, and therefore elastoplastic response of the coating were characterized through H/E, and H3/E2 ratios as a function of the extent of the martensitic transformation. These ratios were correlated to the elastic response and to the resistance to plastic deformation of a surface subjected to sliding mechanical contact, respectively. The usefulness of both ratios to design “hard and tough” coatings, suitable for enhancing of its wear resistance, is compared with the tenacity, G, the semi-quantitative, FT, and the quantitative, KI, fracture toughness values obtained from nano-scratch characterization. Results show that Ti-22Nb-10Zr (wt.%) coating with the highest and lowest hardness and Young's modulus values, and therefore the highest H/E and H3/E2, has the highest cracking resistance and fracture toughness. Under linearly ramped loading from 0.1 to 5 and 100 mN it was impossible to produce fracture of the coating when it was deposited with a bias voltage of −63 V. In return, the coating deposited with a bias voltage of −148 V shows an almost complete elastic recovery until the moment of its fracture and delamination, which is an evidence of its high tenacity and superior fracture toughness. The KI value is ∼21 MPa∗m1/2, which is higher than typical values of bio-ceramics (Al2O3 and ZrO2) used in medical applications, demonstrating that this coating could be used in components subjected to high wear and cyclic impacts, e.g. on femoral heads in artificial hip joints.

Biomaterials, Fracture toughness, Friction coefficient, Low Young's modulus, Non-toxic β-rich Ti coatings, Wear resistance
0169-4332
328-336
Frutos, E.
8730c6ea-7f59-44b7-aa33-cfee57de8b25
Karlik, M.
26f74a9e-c3e3-4f97-8f8d-32a8a6f288a2
Polcar, T.
c669b663-3ba9-4e7b-9f97-8ef5655ac6d2
Frutos, E.
8730c6ea-7f59-44b7-aa33-cfee57de8b25
Karlik, M.
26f74a9e-c3e3-4f97-8f8d-32a8a6f288a2
Polcar, T.
c669b663-3ba9-4e7b-9f97-8ef5655ac6d2

Frutos, E., Karlik, M. and Polcar, T. (2019) The role of α″ orthorhombic phase content on the tenacity and fracture toughness behavior of Ti-22Nb-10Zr coating used in the design of long-term medical implants. Applied Surface Science, 464, 328-336. (doi:10.1016/j.apsusc.2018.09.017).

Record type: Article

Abstract

Tenacity and fracture toughness of a novel β/α″ Ti-22Nb-10Zr (wt.%) coating processed by magnetron sputtering were modified as a result of the martensitic transformation (β → α″) activated by the presence of compressive residual stresses when the coating deposition is performed at high bias voltage values. Mechanical properties, such as hardness, H, and Young's modulus, E, values, and therefore elastoplastic response of the coating were characterized through H/E, and H3/E2 ratios as a function of the extent of the martensitic transformation. These ratios were correlated to the elastic response and to the resistance to plastic deformation of a surface subjected to sliding mechanical contact, respectively. The usefulness of both ratios to design “hard and tough” coatings, suitable for enhancing of its wear resistance, is compared with the tenacity, G, the semi-quantitative, FT, and the quantitative, KI, fracture toughness values obtained from nano-scratch characterization. Results show that Ti-22Nb-10Zr (wt.%) coating with the highest and lowest hardness and Young's modulus values, and therefore the highest H/E and H3/E2, has the highest cracking resistance and fracture toughness. Under linearly ramped loading from 0.1 to 5 and 100 mN it was impossible to produce fracture of the coating when it was deposited with a bias voltage of −63 V. In return, the coating deposited with a bias voltage of −148 V shows an almost complete elastic recovery until the moment of its fracture and delamination, which is an evidence of its high tenacity and superior fracture toughness. The KI value is ∼21 MPa∗m1/2, which is higher than typical values of bio-ceramics (Al2O3 and ZrO2) used in medical applications, demonstrating that this coating could be used in components subjected to high wear and cyclic impacts, e.g. on femoral heads in artificial hip joints.

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More information

Accepted/In Press date: 1 September 2018
e-pub ahead of print date: 5 September 2018
Published date: 15 January 2019
Keywords: Biomaterials, Fracture toughness, Friction coefficient, Low Young's modulus, Non-toxic β-rich Ti coatings, Wear resistance

Identifiers

Local EPrints ID: 426915
URI: http://eprints.soton.ac.uk/id/eprint/426915
ISSN: 0169-4332
PURE UUID: b24a812b-2f3d-4097-8e9f-b6216261d32f
ORCID for T. Polcar: ORCID iD orcid.org/0000-0002-0863-6287

Catalogue record

Date deposited: 14 Dec 2018 17:30
Last modified: 10 Nov 2021 03:28

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Contributors

Author: E. Frutos
Author: M. Karlik
Author: T. Polcar ORCID iD

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