Browsing by Author "Sansom, D."
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Item Effects of ion implantation on Ti-6Al-4V on its frictional behaviour against UHMWPE(1996-09) Alonso, F.; Ugarte, J. J.; Sansom, D.; Viviente, J. L.; Oñate, J. I.; Centros PRE-FUSION TECNALIA - (FORMER); TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOS; Tecnalia Research & InnovationThe aim of this work was to study the effect of carbon ion implantation and a DLC coating on the friction response of T1-6Al-4V/UHMWPE materials used for biomedical implants, and on the endurance of the protective oxide layer of the Ti alloy at increasing loads. Carbon implantation was carried out at doses ranging from 2 × 1017 to 10 × 1017 ions cm-2 and energies from 75 to 180 keV. This implantation procedure produced a more than twofold improvement in hardness, as evaluated by a dynamic micro-indentation technique at increasing loads from 0.4 to 10 mN. Dry pin-on-disc tribological tests, using an UHMWPE pin, showed that some of the implantation treatments effectively protected the surface of the Ti alloy, without producing a break in the protective passive oxide layer and exhibited low friction values, similar to those obtained in DLC coatings. No direct correlation has been found, however, between the hardening induced by ion implantation and the improved tribological response. Formation of TiC precipitates could account for the hardening effect observed after carbon implantation and, in addition, implantation may cause stabilisation of the protective oxide layer on the titanium surface.Item Ion implantation of TiN films with carbon or nitrogen for improved tribomechanical properties(1996-10) Sansom, D.; Viviente, J. L.; Alonso, F.; Ugarte, J. J.; Oñate, J. I.; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOS; Centros PRE-FUSION TECNALIA - (FORMER); Tecnalia Research & InnovationIn the field of engineering materials, the study of titanium nitride (TiN) films has attracted great interest because of its unique combination of properties. This paper is concerned with the implantation of nitrogen or carbon ions into TiN films to evaluate and obtain the optimum conditions for increased tribological resistance. A commercially available titanium nitride coating produced by ion plating, of approximately 3.5 μm thickness, was treated by implantation of nitrogen or carbon ions at energies of 100 and 75 keV, respectively. The dose range was between 5 × 1016 and 1 × 1018 ions cm-2. It has been observed that a suitable implantation procedure can lead to a maximum hardness improvement of about 15%, as evaluated with a dynamic micro-indentation method at loads from 0.4 to 10 mN. Wear tests performed on an unlubricated reciprocating apparatus, using an alumina ball with a load of 9.8 N and at a speed of 150 cycles min-1, showed that implantation of nitrogen and carbon can reduce wear by 22% and 42%, respectively. Small-area X-ray photoelectron spectroscopy (SAXPS) was used to evaluate the concentration of implanted elements as a function of depth. The analysis showed that in the high-dose C+-implanted sample a very high percentage of the carbon remained as pure carbon, whereas in the lower-dose C+-implanted sample the carbon stayed mainly in a carbidic form. In the case of nitrogen implantation, no large variations in the state or concentrations were recorded.Item Zinc coatings on steel produced by ion beam assisted deposition(1996-10) Sansom, D.; Alonso, F.; Ugarte, J. J.; Zapirain, F.; Oñate, J. I.; Centros PRE-FUSION TECNALIA - (FORMER); Tecnalia Research & InnovationWorld-wide, only about 30% of cold-rolled products are coated by conventional methods such as hot-dip galvanising and electrodeposition. The demand for coated steel strip is expected to increase in the next few years and it has been demonstrated that dry PVD technologies can be applied continuously or in a semi-continuous way to produce corrosion-resistant coatings with excellent properties and performance. PVD technologies are also attractive because of reduced environmental constraints compared with conventional methods. Ion beam assisted deposition (IBAD), a relatively new PVD technique, offers the possibility of controlling process parameters independently, and can produce coatings with tailored properties. The aim of this work has been to evaluate the use of IBAD as a prospective method to produce Zn coatings on steel strip. Zinc coatings were deposited by IBAD onto 1 mm IF-steel sheet, at a thickness of approximately 5 μm. Various angles (10°-50° to the ion beam), evaporation rates (1-3 nm s-1) and ion beam energies (500-1000 eV) were selected, while the beam intensity was kept constant at 25 mA. This was to maintain the I/A arrival ratio at a sufficiently low value to obtain good deposition rates when taking into account sputtering effects. A bending test was conducted to test the formability of the coating. Any cracking or delamination that occurred was observed under an optical microscope and a chemical test was used to determine the amount of revealed substrate. This test showed the lack of interconnected pores in the Zn coatings. Furthermore, all IBAD films showed good adhesion and formability with no signs of delamination. Topographical observation of the coatings was undertaken using SEM, which was also used to study the coating thickness and uniformity. These observations showed the deposited coatings to be uneven and of widely varying thicknesses. These variations are discussed in terms of the effects of sputtering and evaporator-substrate distance. From SEM micrographs it could be seen clearly that ion bombardment during deposition influences the structure of the produced film, changing the structure from a highly columnar growth to a fine, even-grained structure. The corrosion resistance was tested using a standard ASTM B117 salt spray test, with a 3.5% NaCl salt solution. This test showed a dependence of the corrosion resistance on the film thickness, with little variations due to the different morphology or microstructure of the films.