Its The Drive Cone Cavity Engineering Essay Essays -

Its The Drive Cone Cavity Engineering Essay The drive cone cavity is one of the hottest un-cooled components in the engine. Operating around 900k at 10,000 rpm, the material used in making the drive cone is operating at edge of its safe working temperature changes at these high temperatures. A 10 K rise in shaft temperature can reduce the life of the shaft. The temperature must therefore be predicted to within 10 K or better to guarantee accurate stress predictions. It the thermal model cannot guarantee the 10 K accuracy required, a much shorter component life would have to be declared or alternative materials must be found. This report contains the different type of the materials which can be used to enhance the performance of the drive cone cavity and in order to do so the criteria is sub-divided into four group Trends in aero-engine materials use As shown in Fig 2 the trends in increase of high temperature materials for gas turbine part. Although there are many monolithic ceramics materials show evidence of fundamental properties, but the main issue is relative to their application in aero engines has been their flaw sensitivity and brittle fracture modes. In addition fibre CMCs are very appealing materials due to (i) their high temperature performance as compared with other super alloys and (ii) their higher fracture toughness relate with monolithic ceramics in aero engines, in which structural reliability is most required. For that reason, CMCs are potential materials to meet these requirements in drive cone cavity. Most of the improvement in material for gas turbine component has been associated with the nickel base alloy system since of the ability to achieve better strength with this system. These alloys form gamma-prime second phase particles in heat treatment, which impart very high strengths to the alloy. Gamma-prime has the common composition of X3Z, where X is mainly Ni, and Z is mostly Al and Ti. (Gamma-prime is generally written as Ni3 (Al,Ti)). Ta and Cb can replace with Al and Ti, and Co can substitute for Ni. As a result, a more correct formula would be (Ni, Co)3 (Al, Ti, Ta, Cb). The gamma-prime alloys can be either cast or wrought. The cast forms are more common because of the economies of casting difficult shapes, the capability to uphold very high mechanical properties by vacuum casting, and the complications appear when forging metals having exceptional mechanical properties at high temperatures. In addition to the structure of gamma-prime particles, which is the principal strengthening mechanism, these alloys also incorporate strengthening by solid solution hardening and carbide formation. The gamma-prime super alloys are composed of many alloying elements. Chromium is used for resistance to environmental attack. Aluminium and tantalum assist in the resistance to environmental attack. Cobalt is used to stabilise the microstructure. Aluminium, titanium, tantalum and columbium are elements that form gamma- prime. Refractory elements, such as tungsten, molybdenum, tantalum and columbium are used for solid solution hardening. (Note: Chromium and cobalt also contribute to solid solution hardening.) These same elements, along with chromium, form carbides with the carbon that is added to the alloy. These carbides primarily strengthen the grain boundaries. In addition to these major elements, there are several elements added in minute quantities (sometimes called fairy dust) that strengthen the grain boundaries. These elements include boron, hafnium and zirconium. The microstructure of a common gamma-prime alloy, IN-738. Nickel base superalloys can be classified into solid solution alloys, and gamma-prime (or precipitation hardened) alloys. The solid solution alloys, which can be either cast or wrought, contain few elements that form gamma-prime particles. Instead, they are solid solution strengthened by refractory elements, such as tungsten and molybdenum, and by the formation of carbides. They also contain chromium for protection from hot corrosion and oxidation, and cobalt for microstructural stability. Because these alloys are not precipitation hardened, they are readily weldable. Common examples of these alloys are Hastelloy X, Nimonic 263, IN-617, and Haynes 230. The microstructure of IN-617 is shown in Figure 3. Furthermore, the superalloys are relatively expensive, heavy and difficult to fabricate and machine. In light of these limitations, other materials approaches are being pursued. Titanium is a plentiful, low density (4.5 gm/cm3) [4] element having a high melting temperature (1668C) [4] and a