Study of Titanium Nitrides Synthesized by High Dose Ion Implantation
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ABSTRACT Polycrystalline titanium samples were implanted with N+ ions at high fluences and at several energies. The aim was to obtain 4000 A thick nitrided layers of constant nominal concentration equal to 20% ,30%, and 40%.
The results obtained by RBS showed a flat nitrogen distribution with depth and the measured concentrations were respectively 20%/o,3 1% and 38%. X-ray grazing incidence diffraction indicated that, at 20%, a nitrogen solid solution is formed in the xc-Ti matrix. At 31% the nitrogen solid solution is present besides a 6-TiN phase and at 38% only the 5-TiN phase remains. From nanoindentation measurements, we derived the depth-related hardness and Young's modulus of the implanted samples. These values were compared to those found on titanium nitride layers obtained with other coating techniques.
INTRODUCTION Titanium and its alloys gave rise to important research during the last ten years in the
biomedical field [1-3], especially for the dental and orthopedic prosthesis. Indeed, these materials have very interesting properties: low density, high corrosion resistance in several environments and good mechanical properties. Nevertheless, they present also weak tribological characteristics, especially in the field of friction and wear resistance [4,5]. One of the solutions to improve these characteristics consists in covering these materials with nitride, carbide or boride layers in order to increase their surface hardness. Indeed, the hardness increment is usually correlated with an improvement of all forms of wear resistance. For this purpose, the ionic implantation is one of the best technique as it offers many advantages compared to the other surface treatments[6,7],. Especially, the absence of an abrupt interface removes completely the adherence problems of the created layers. Our work concerns the ionic nitrogen implantation in pure titanium. The implantations were performed at several energies in order to obtain uniform nitrogen concentration equal to 20%, 30% and 40% over a depth of about 400 nm. The experimental nitrogen profiles were determined by RBS. The phases identification was done by grazing incidence X ray diffraction. And finally, the hardness and the Young's modulus were measured by nanoindentation.
243 Mat. Res. Soc. Symp. Proc. Vol. 354 01995 Materials Research Society
EXPERIMENTAL TECHNIQUES Samples preparation and ion implantation The rectangular samples (10 x 15 mm.) were obtained from a titanium sheet, then polished mechanically, first with carborundum then with diamond paste until 0.25ptm. Finally, they were washed with ethanol in an ultrasonic receiver. Ion implantation was performed with an EATON 200 MC implanter, equipped with a magnetic mass separator. Besides, an electrostatic scanning system allowed t
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