Fibre Laser Nitriding of Titanium and its Alloy in Open Atmosphere for Orthopaedic Implant Applications: Investigations on Surface Quality, Microstructure and Tribological Properties

Hdl Handle:
http://hdl.handle.net/10034/620303
Title:
Fibre Laser Nitriding of Titanium and its Alloy in Open Atmosphere for Orthopaedic Implant Applications: Investigations on Surface Quality, Microstructure and Tribological Properties
Authors:
Chan, Chi-Wai; Lee, Seunghwan; Smith, Graham C.; Donaghy, Clare
Abstract:
Laser nitriding is known to be an effective method to improve the surface hardness and wear resistance of titanium and its alloys. However, the process requires a gas chamber and this greatly limits the practicability for treating orthopaedic implants which involve complex-shaped parts or curved surfaces, such as the tapered surface in a femoral stemor the ball-shaped surface in a femoral head. To tackle this problem, a direct laser nitriding process in open atmosphere was performed on commercially pure titanium (grade 2, TiG2) and Ti6Al4V alloy (grade 5, TiG5) using a continuous-wave (CW) fibre laser. The effects of varying process parameters, for instance laser power and nitrogen pressure on the surface quality, namely discolouration were quantified using ImageJ analysis. The optimised process parameters to produce the gold-coloured nitride surfaces were also identified: 40W(laser power), 25mm/s (scanning speed), 1.5mm(standoff distance) and 5 bar (N2 pressure). Particularly, N2 pressure at 5 barwas found to be the threshold above which significant discolouration will occur. The surface morphology, composition, microstructure, micro-hardness, and tribological properties, particularly hydrodynamic size distribution of wear debris, were carefully characterized and compared. The experimental results showed that TiG2 and TiG5 reacted differently with the laser radiation at 1.06 μm wavelength in laser nitriding as evidenced by substantial differences in the microstructure, and surface colour and morphology. Furthermore, both friction andwear properties were strongly affected by the hardness and microstructure of titaniumsamples and direct laser nitriding led to substantial improvements in their wear resistant properties. Between the two types of titanium samples, bare TiG2 showed higher friction forces and wear rates, but this trend was reversed after laser nitriding treatments.
Affiliation:
Queens University Belfast (Chan, Donaghy), Technical University Denmark (Lee), University of Chester (Smith)
Citation:
Chan, C., Lee, S., Smith, G. C. & Donaghy, C. (2016). Fibre Laser Nitriding of Titanium and its Alloy in Open Atmosphere for Orthopaedic Implant Applications: Investigations on surface quality, microstructure and tribological properties. Surface and Coatings Technology, 309, 628-640.
Publisher:
Elsevier
Journal:
Surface and Coatings Technology
Publication Date:
20-Dec-2016
URI:
http://hdl.handle.net/10034/620303
DOI:
10.1016/j.surfcoat.2016.12.036
Additional Links:
http://www.sciencedirect.com/science/article/pii/S025789721631324X
Type:
Article
Language:
en
ISSN:
0257-8972
EISSN:
1879-3347
Appears in Collections:
Natural Sciences

Full metadata record

DC FieldValue Language
dc.contributor.authorChan, Chi-Waien
dc.contributor.authorLee, Seunghwanen
dc.contributor.authorSmith, Graham C.en
dc.contributor.authorDonaghy, Clareen
dc.date.accessioned2016-12-21T09:25:29Z-
dc.date.available2016-12-21T09:25:29Z-
dc.date.issued2016-12-20-
dc.identifier.citationChan, C., Lee, S., Smith, G. C. & Donaghy, C. (2016). Fibre Laser Nitriding of Titanium and its Alloy in Open Atmosphere for Orthopaedic Implant Applications: Investigations on surface quality, microstructure and tribological properties. Surface and Coatings Technology, 309, 628-640.en
dc.identifier.issn0257-8972-
dc.identifier.doi10.1016/j.surfcoat.2016.12.036-
dc.identifier.urihttp://hdl.handle.net/10034/620303-
dc.description.abstractLaser nitriding is known to be an effective method to improve the surface hardness and wear resistance of titanium and its alloys. However, the process requires a gas chamber and this greatly limits the practicability for treating orthopaedic implants which involve complex-shaped parts or curved surfaces, such as the tapered surface in a femoral stemor the ball-shaped surface in a femoral head. To tackle this problem, a direct laser nitriding process in open atmosphere was performed on commercially pure titanium (grade 2, TiG2) and Ti6Al4V alloy (grade 5, TiG5) using a continuous-wave (CW) fibre laser. The effects of varying process parameters, for instance laser power and nitrogen pressure on the surface quality, namely discolouration were quantified using ImageJ analysis. The optimised process parameters to produce the gold-coloured nitride surfaces were also identified: 40W(laser power), 25mm/s (scanning speed), 1.5mm(standoff distance) and 5 bar (N2 pressure). Particularly, N2 pressure at 5 barwas found to be the threshold above which significant discolouration will occur. The surface morphology, composition, microstructure, micro-hardness, and tribological properties, particularly hydrodynamic size distribution of wear debris, were carefully characterized and compared. The experimental results showed that TiG2 and TiG5 reacted differently with the laser radiation at 1.06 μm wavelength in laser nitriding as evidenced by substantial differences in the microstructure, and surface colour and morphology. Furthermore, both friction andwear properties were strongly affected by the hardness and microstructure of titaniumsamples and direct laser nitriding led to substantial improvements in their wear resistant properties. Between the two types of titanium samples, bare TiG2 showed higher friction forces and wear rates, but this trend was reversed after laser nitriding treatments.en
dc.language.isoenen
dc.publisherElsevieren
dc.relation.urlhttp://www.sciencedirect.com/science/article/pii/S025789721631324Xen
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/4.0/en
dc.subjectfibre laseren
dc.subjectlaser nitridingen
dc.subjecttitanium alloysen
dc.subjectwear debrisen
dc.subjectorthopaedic implantsen
dc.titleFibre Laser Nitriding of Titanium and its Alloy in Open Atmosphere for Orthopaedic Implant Applications: Investigations on Surface Quality, Microstructure and Tribological Propertiesen
dc.typeArticleen
dc.identifier.eissn1879-3347-
dc.contributor.departmentQueens University Belfast (Chan, Donaghy), Technical University Denmark (Lee), University of Chester (Smith)en
dc.identifier.journalSurface and Coatings Technologyen
dc.date.accepted2016-12-09-
or.grant.openaccessYesen
rioxxterms.funderpart-funded by Queens University Belfast start-up grant D8201MASen
rioxxterms.identifier.projectunfundeden
rioxxterms.versionAMen
rioxxterms.licenseref.startdate2018-12-20-
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