title: Processing of an ultrafine-grained titanium by high-pressure torsion: an evaluation of the wear properties with and without a TiN coating.
abstract: A commercial purity (CP) Grade 2 Ti was processed by high-pressure torsion (HPT) using an imposed pressure of 3.0GPa at room temperature. The HPT processing reduced the grain size from ∼8.6 μm in the as-received state to ultra-fine grains (UFG) of ∼130 nm after HPT. Tensile testing showed the HPT-processed Ti exhibited a good combination of high ultimate tensile strength (∼940 MPa) and a reasonable elongation to failure (∼23%). Physical vapour deposition was used to deposit TiN coatings, with a thickness of 2.5 μm, on Ti samples both with and without HPT processing. Scratch tests showed the TiN coating on UFG Ti had a critical failure load of ∼22.5 N whereas the load was only ∼12.7 N for the coarse-grained Ti. The difference is explained using a simple composite hardness model. Wear tests demonstrated an improved wear resistance of TiN coating when using UFG Ti as the substrate. The results suggest that CP Ti processed by HPT and subsequently coated with TiN provides a potentially important material for use in bio-implants.
authors.affiliation: National Centre for Advanced Tribology at Southampton, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK.
authors.forename: Chuan Ting
authors.initials: CT
authors.lastname: Wang
authors.forename: Nong
authors.initials: N
authors.lastname: Gao
authors.forename: Mark G
authors.initials: MG
authors.lastname: Gee
authors.forename: Robert J K
authors.initials: RJ
authors.lastname: Wood
authors.forename: Terence G
authors.initials: TG
authors.lastname: Langdon
mesh_terms: D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D008422:Materials Testing; D055595:Mechanical Phenomena; D011312:Pressure; D013696:Temperature; D014025:Titanium / Q000737:chemistry*
chemical_list: D020099:Coated Materials, Biocompatible; C041500:titanium nitride; D014025:Titanium