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Last Stages and Exhaust Hoods of LP Cylinders
Published in Alexander S. Leyzerovich, Steam Turbines for Modern Fossil-Fuel Power Plants, 2021
For full-speed LSBs, there are no in sight other real ways to increase radically their length and annular exit area than by transition to manufacturing the blades from titanium alloys (for example, Ti-5Al, Ti-6Al-4V, or Ti-6Al-6V-2Sn). As a rule, titanium-alloy blades are merely coined “titanium.” The density of titanium alloys is approximately 1.8 times less that that of steel, with the same, or even greater, strength. Because of this, the length of titanium buckets can be extended appreciably. On the other hand, titanium alloys are considerably more expensive compared to steel and are much harder in machining. Nevertheless, even the most consistent former opponents of titanium LSBs have presently turned to developing and implementing them, and every major turbine producer in the world employs or, at least, has at its disposal titanium LSBs commercially available. Effectiveness of titanium LSB has been well proved in the operational practice since the very early 1980s.4-12 An appearance of a characteristic 1,093-mm (43-in) titanium LSB for the rotation speed of 3,000 rpm developed by Hitachi is shown in Figure 5-3.13
Tungsten Inert Gas Welding
Published in P. Chakravarthy, M. Agilan, N. Neethu, Flux Bounded Tungsten Inert Gas Welding Process, 2019
P. Chakravarthy, M. Agilan, N. Neethu
This method is also known as the InterPulse welding technique developed by VBC Group, UK. InterPulse operates at very high frequency (20,000 Hz) and produces a magnetically constricted columnar profiled arc similar to the plasma arc, which significantly reduces the overall heat input during welding. Due to very low heat input, the cross-sectional area of the weld is reduced. The technique was originally developed to weld nickel-based superalloys and was subsequently extended to titanium alloys. This technique is also recommended to repair the un-weldable and precision superalloy castings and produces a narrow weld bead and heat-affected zone. Due to a focused arc and low heat input in this technique, titanium alloys can be successfully welded in the shop floor instead of welding in costly and capital-intensive welding chambers and trailing shields.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
Titanium alloys are primarily Ti-6Al-4V (i.e., 6% aluminum, 4% vanadium, and 90% titanium). Pure titanium is also used, primarily in dental applications. As with cobalt-chrome alloys and stainless steel, titanium and its alloys offer excellent biocompatibility and corrosion resistance. In fact, the titanium oxide TiO2 passive layer formed on the surface of these alloys increases the resistance to corrosion compared to that of the other implant metals. Titanium alloys are becoming increasingly popular in orthopedics because their strength is as good as the other metal implant materials, but they are only half as stiff (TABLE 216.1). This is potentially important because a large elastic modulus mismatch between implant and bone causes stress concentrations in some places and tends to stress shield the bone in others. However, the modulus of titanium alloys is still several times greater than that of bone (Tables 216.1 and Table 216.3), and marked decreases in stress shielding when these alloys are used have not yet been demonstrated. Titanium alloys are also sensitive to notching. A notch or scratch on titanium alloy implants will significantly reduce their fatigue life.
Performance evaluation of process parameters using MCDM methods for Titanium Alloy (Ti6al4v) in turning operation
Published in Australian Journal of Mechanical Engineering, 2023
Sushil V Ingle, Dadarao N Raut
Titanium and its alloys have outstanding corrosion resistance, superior biocompatibility, notable tissue inertness, good weldability, and other properties (Bhaumik, Divakar, and Singh 1995; von Turkovich and Durham 1982). These alloys have several uses in a variety of industries, including the chemical processing industry, the oil and gas industry, the marine and aviation industries, and the medical sector (2005). The aforementioned intrinsic qualities and practicality of titanium alloys compel researchers to investigate and scrutinise a variety of these alloys’ machining features. Recent years have seen increased interest from other commercial and industrial sectors in the studies on the machinability characteristics of these alloys. On the other hand, the restricted use of titanium alloys is caused by their high initial cost and extraction process challenges. Additionally, due to the lower productivity, these alloys can only be machined at a limited range of cutting rates (about 30–60 m/min) due to their high chemical affinity and poor heat conductivity.
A review on parameters affecting properties of biomaterial SS 316L
Published in Australian Journal of Mechanical Engineering, 2022
In the past titanium alloys were most widely used for biomedical applications. Replacement of failed tissue by medicine is possible using implant devices. Examples consist of screws for fracture fixation, artificial hearts, artificial hip joints, bone plates, and artificial knee joints. Titanium alloys available are alpha (α) alloys, beta (β) alloys, and alpha-beta alloys. α alloys offer high creep strength, oxidation resistance but these are non-heat treatable which can be overcome by using β alloys which have excellent formability and also responsive to heat treatment because of this α-β titanium alloys are recommended materials (Wanhill and Barter 2012). Most widely used titanium alloys are Ti-6Al-4V, Ti-6Al-7Nb (ASTM F1295), Ti-12Mo-6Zr (ASTM F1813) and Ti-13Nb-13Zr (ASTM F1713). Large number of universities and industries had performed in-vivo and in-vitro titanium experiments throughout the world for the last 50 years. From their research, it has been found that biocompability of titanium is associated with its oxides. Commercially pure titanium surface spontaneously build-up stable and inert oxide layer, due to which it is considered to be the best biocompatible metallic material. Biocompatibility of titanium alloys depends on thermodynamic state at physiological pH values, ion formation tendency in aqueous environments, corrosion resistance, level of electronic conductivity, and an isoelectric point of oxide (Elias et al. 2008), (Casaletto et al. 2001).
Tribological Performance of Gradient Ag-Multilayer Graphene/TC4 Alloy Self-Lubricating Composites Prepared By Laser Additive Manufacturing
Published in Tribology Transactions, 2021
Hongyan Zhou, Chaohua Wu, Dong-yan Tang, Xiaoliang Shi, Yawen Xue, Qipeng Huang, Jin Zhang, Ammar H. Elsheikh, Ahmed Mohamed Mahmoud Ibrahim
Titanium alloys are excellent candidates in the fields of aerospace, automobile industry, offshore engineering, and medical equipment, due to their low density, high strength, favorable corrosion resistance, and remarkable biocompatibility (1, 2). Especially, many core components of aero engines and structural parts of aircraft, as well as more than 95% of fasteners on the aircraft, have been made of titanium alloys (3, 4). Nowadays, the rapid development of high thrust-to-weight ratio aero engines creates an increasing demand for titanium alloys. However, titanium alloys with inferior tribological properties such as high friction coefficient, serious adhesive wear, and fretting wear have been unable to meet the tough working conditions, as well as to be used as friction components (5–7). Therefore, it is important to enhance the tribological properties of titanium alloys to make them more safely and widely used in advanced aero engines under the tough working conditions of high alternating load and high working temperature.