Papers by Keyword: Ti₆Al₄V

Abstract: Ti6Al4V is a difficult to machine alloy with low cutting efficiency and server tool wear. A series of orthogonal turning tests with CBN (Cubic Boron Nitride) in higher speed scale was carried out on a CA6140 lathe. The experiential functions of tool life based on orthogonal experiment were developed. The tool wear morphologies were examined by scanning electron microscope (SEM) and energy disperse spectroscopy (EDS), adhesion, diffusion and micro-chipping were the major wear mechanisms of CBN tool. Finally, the cutting parameters of CBN tool in Ti6Al4V dry turning were optimized based on tool life-efficiency contour analysis, in same cutting efficiency, the higher cutting speed and small depth of cut are the better selection, it means that utilization of CBN tool enables the high cutting speed turning of Ti6Al4V.

Abstract: The Mo surface modified layer on Ti6Al4V alloy was obtained by the plasma surface alloying technique. The structure and composition of the Mo modified Ti6Al4V alloy was investigated by X-ray diffraction (XRD) and glow discharge optical emission spectroscopy (GDOES). The Mo modified layer contains Mo coating on subsurface and diffusion layers between the subsurface and substrate. The X- ray diffraction analysis of the Mo modified Ti6Al4V alloy reveals that the outmost surface of the Mo modified Ti6Al4V alloy is composed of pure Mo. The electrochemical corrosion performance of the Mo modified Ti6Al4V alloy in 25°C Hank’s solution was investigated and compared with that of Ti6Al4V alloy. Results indicate that the self-corroding electric potential and the corrosion-rate of the Mo modified Ti6Al4V alloy are higher than that of Ti6Al4V alloy in 25°C Hank’s solution.

Abstract: Ti6Al4V alloy is promising biology material with outstanding properties of low density, high specific strength, and exceptional corrosion resistance. However, one of its disadvantages is the poor tribological property. In this paper Mo-N hard surface modification layers were formed on Ti6Al4V at 900°C substrate temperature by plasma reactive sputtering. The flux ratio N2/Ar is an important parameter and its influence on the composition, structure and hardness of the Mo-N layers is studied. The Mo-N layers are duplex layers, composed of diffusing layer and surface coating. The component of Mo and N elements in the diffusing layer changes gradually which can enhance the load-bearing capacity to the coating and ensure the durability of the coating. With the increase of the flux ratio N2/Ar, the content of N element in the Mo-N layers increases. The Mo-N layers were polycrystalline γ- Mo2N with (200) plane oriented parallel to the substrate surface. The surface hardness of the formed layers is in the range HK1330-1430. The hardness of the Mo-N layers increases with the increase of the flux ratio N2/Ar and the reason is that the content of N element in the Mo-N layers increases.

Abstract: The titanium affinity by oxygen is one of main factors that limit the application of their alloys as structural materials at high temperatures. The objective of this work was evaluating the microstructure of the of the zirconia plasma sprayed coating Ti-6Al-4V alloy in creep test. Yttria (8 wt.%) stabilized zirconia (YSZ) (Metco 204B-NS) with a CoNiCrAlY bond coat (AMDRY 995C) was atmospherically plasma sprayed on Ti-6Al-4V substrates by Sulzer Metco. Constant load creep tests were conducted with Ti-6Al-4V alloy in air and in nitrogen atmospheres in uncoated samples and in air in coated samples at stress level of 56 MPa at 700°C. The microstructural analyze show that the predominant mechanism in the test conditions was characterized by formation and coalescence of micro cavities with shape and size varieties. The cavities are corrugated in discontinue regions, like inclusions and points involving dislocation. The size and shape of dimples are governed by number and distribution of nucleated micro cavities and by stress internal level present in the material.

Abstract: Due to their high hardness and wear resistance, Si3N4 based ceramics are one of the most suitable cutting tool materials for machining cast iron, nickel alloys and hardened steels. However, their high degree of brittleness usually leads to inconsistent results and sudden catastrophic failures. This necessitates a process optimization when machining superalloys with Si3N4 based ceramic cutting tools. The tools are expected to withstand the heat and pressure developed when machining at higher cutting conditions because of their high hardness and melting point. This paper evaluates the performance of α-SiAlON tool in turning Ti–6Al–4V alloy at high cutting conditions, up to 250 m min−1, without coolant. Tool wear, failure modes and temperature were monitored to access the performance of the cutting tool. Test results showed that the performance of α-SiAlON tool, in terms of tool life, at the cutting conditions investigated is relatively poor due probably to rapid notching and excessive chipping of the cutting edge. These facts are associated with adhesion and diffusion wear rate that tends to weaken the bond strength of the cutting tool.

Abstract: Thermomechanical and electrical properties of zirconia-based ceramics have led to a wide range of advanced and engineering ceramic applications like solid electrolyte in oxygen sensors, fuel cells and furnace elements and its low thermal conductivity has allowed its use for thermal barrier coatings for aerospace engine components. A comparison between CoNiCrAlY bond coat and zirconia plasma sprayed coatings on creep tests of the Ti-6Al-4V alloy was studied. The material used was commercial Ti-6Al-4V alloy. Yttria (8 wt.%) stabilized zirconia (YSZ) with a CoNiCrAlY bond coat was atmospherically plasma sprayed on Ti-6Al-4V substrates by Sulzer Metco Type 9 MB. Constant load creep tests were conducted on a standard creep machine in air on coated samples, at stress levels of 520 MPa at 500°C to evaluate the oxidation protection on creep of the Ti-6Al-4V alloy. Results indicate that the creep resistance of the ceramic coating was greater than metallic coating.

Abstract: Ti-6Al-4V ELI (extra low interstitials) was processed by equal channel angular pressing in order to obtain an ultrafine-grained (UFG) microstructure which is known to enhance the fatigue behavior of metallic materials. Fatigue properties of UFG Ti-6Al-4V ELI were studied by strain and stress controlled fatigue tests. UFG Ti-6Al-4V ELI shows an improvement of the fatigue behavior compared to conventional grain (CG) size counterpart. Microstructural investigations prior to and after fatigue testing confirm a high structural stability of the UFG material. Hence, the UFG alloy has a high potential for prospective use in biomedical and engineering applications.

Abstract: To improve the biocompatibility and bioactivity of titanium and titanium alloys, a titanium oxide layer was synthesized on Ti, Ti-6Al-4V and NiTi shape memory alloy (SMA) using a H2O2-oxidation and hot water aging technique. The surface of these metals before and after the oxidation treatment was characterized using scanning electron microscopy and energy dispersive X-ray spectroscopy. Because of the synthetic titanium oxide surface layer, the Al and V contents on the surface of as-oxidized Ti-6Al-4V decreased significantly. Similarly, the Ni content on the surface of as-oxidized NiTi SMA was also significantly reduced. Potentiodynamic polarization curves indicated that the synthetic titania layer was more chemically stable than the spontaneous titania film on the metals. Among the three metals, the oxide layer on Ti was the most stable chemically. The in vitro bioactivity of as-oxidized metals was assessed through incubation in simulated body fluid (SBF). Compared to as-oxidized Ti-6Al-4V and NiTi SMA, as-oxidized Ti was the most bioactive.

Abstract: This paper introduced the machinability and the state-of-art of Ti6Al4V machining. Turning test with thee different tungsten carbide tool have be done at cutting speed 40, 80, 120, 160 m/min, the relationship between cutting force and cutting speed, cutting distance was analyzed, the influence of working cutting edge angle on the tool wear and cutting force was investigated as well. Finally, the tool wear and wear mechanics was analyzed.

Abstract: It is well known that the utilization of superplastic characteristics in manufacturing process makes many of aerospace components lighter and stiffer. The weight saving is vitally important especially for aerospace application and even more weight saving is possible when the superplastic forming is carried out with diffusion bonding. In this study, the lightweight sandwich structure was fabricated with superplastic forming(SPF) process from diffusion bonded(DB) Ti-6Al-4V sheets. The solid state diffusion bonding process was conducted in non-vacuum environment under a pressure of 4MPa for 60 minutes at 875°C and the superplastic forming process was followed for another 40 minutes. Good solid state bonding interface have been observed in microstructure observation and the sandwich structure was successfully manufactured. It is important to note that the forming conditions of present study are more practical for application than the previously published conditions, which require vacuum environment, higher temperature and/or pressure.