Titanium superalloys

The United States has to import all the cobalt it uses. One of the most important applications of cobalt is in the production of superalloys. These superalloys consist primarily of iron, cobalt, or nickel, with small amounts of other metals, such as chromium, tungsten, aluminum, and titanium. Superalloys are resistant to corrosion (rusting) and retain their properties at high temperatures. Superalloys are used in jet engine parts and gas turbines. 

Description and General Properties. Metal matrix composites (MMCs) consist of a metal or an alloy matrix with a reinforcement material (e.g., particulates, monofilaments, or whiskers). The matrix alloy, the reinforcement material, the volume and shape of the reinforcement, the location of the reinforcement, and the fabrication method can all be varied to achieve required properties. Most of the metal-matrix composites are made of an aluminum matrix. But aluminum-matrix composites must not be considered as a single material but as a family of materials whose stiffness, strength, density, and thermal and electrical properties can be tailored. Moreover a growing number of applications require improved matrix properties and therefore, metal matrices of magnesium, titanium, superalloys, copper, or even iron are now available commercially. Compared to bulk metals and their alloys, MMCs offer a number of advantages such as ... 

Niobium is important as an alloy addition in steels (see Steel). This use consumes over 90% of the niobium produced. Niobium is also vital as an alloying element in superalloys for aircraft turbine engines. Other uses, mainly in aerospace appHcations, take advantage of its heat resistance when alloyed singly or with groups of elements such as titanium, tirconium, hafnium, or tungsten. Niobium alloyed with titanium or with tin is also important in the superconductor industry (see High temperature alloys Refractories). 

Detailed consideration of the structure of many of the advanced and complex alloys which are of considerable technological importance (high-strength titanium alloys, nickel-base superalloys, etc.) is beyond the scope of this section, other than to point out that no new principles are involved. Certain titanium alloys, for example, exhibit a martensitic transformation, while many nickel-base superalloys are age hardening. Similarly, cast irons, although by no means advanced materials, are relatively complex they are considered in Section 1.3 where graphitisation is discussed. 

Nickel barium titanium primrose priderite, formula and DCMA number, 7 347t Nickel-based alloys, properties of, 77 848t Nickel-base superalloys, 77 103 Nickel battery technology, 77 111 Nickel-beryllium alloys, 3 656-659 Nickel-boron deposition, 9 693-695, 708 Nickel brass, corrosion, 7 812 Nickel bromide, 77 110... 

This process, originally designated as RSR (rapid solidification rate), was developed by Pratt and Whitney Aircraft Group and first operated in the late 1975 for the production of rapidly solidified nickel-base superalloy powders.[185][186] The major objective of the process is to achieve extremely high cooling rates in the atomized droplets via convective cooling in helium gas jets (dynamic helium quenching effects). Over the past decade, this technique has also been applied to the production of specialty aluminum alloy, steel, copper alloy, beryllium alloy, molybdenum, titanium alloy and sili-cide powders. The reactive metals (molybdenum and titanium) and... 

In a pilot plant [2,13], superalloy scrap containing Mo, W, Cr, Fe, Co, and Ni is pretreated in a furnace with carbon to transfer refractory metals (Mo, W, etc.) into carbides. The melt is granulated and the resulting material is charged into titanium baskets. Diaphragm-type electrolytic cells are used for anodic dissolution of the granulated material. Fe, Co, Ni, and small amounts of Cr are dissolved into a calcium chloride solution by the current. The metal carbides are not dissolved and remain as an anodic residue in the baskets. 

Often there is a borrowing of terms between metal-intense materials science and polymer-intense materials science where there is actually little relationship between the two. This is not the case with metal-matrix composites (MMCs). Although the materials are often different, there are a number of similarities. For polymer-intense composites, the matrix materials are organic polymers. For MMCs, the matrix materials are typically a metal or less likely an alloy. Popular metals include aluminum, copper, copper-alloys, magnesium, titanium, and superalloys. ... 

Silicon carbide fibers have been used with aluminum, titanium, and coball-based superalloys for high-temperature structures and engine components. 

Mew Materials and Processes. New materials and processes include aligned eutectics, oxide and liber-reinforced superalloys, intermelalhc compounds and other ordered phases including titanium aluminidcs. nickel aluminides. and iron aluminidcs. 

A nickel-base superalloy having special utility in the production of single crystal gas turbine engine blades consisting essentially of about 1 to 3 percent rhenium, about 14 percent chromium, about 9.5% cobalt, about 3.8% tungsten, about 2 percent tantalum, about 1.5% molybdenum, about 0.05% carbon, about 0.004% boron and respectively, from about 3 to 4.8% aluminum, from about 4.8% to about 3 percent titanium, and balance substantially nickel. 

Table 1 lists a variety of environments that can be considered extreme and are the subject of chemical studies. It is difficult to develop general quantitative criteria as to what constitutes an extreme environment. Such categorizations must be viewed from the perspective of the type of system under consideration. For a liquid lubricant in an engine, a temperature of 620 K, above its decomposition temperature, is an extreme environment. For metals exposed to high temperatures, such as titanium and nickel superalloys in aerospace vehicles, temperatures of 1100 and 1400 K, respectively, test their operational limits. In these two cases, thermal degradation of the... 

High-purity metals and superalloys are required for the aeronautics, electronics, instruments, space, and defense industries the raw materials are at present imported. Primarily, these special metals include nickel-and cobalt-based superalloys, high-strength iron-based alloys, titanium-based alloys, controlled-expansion alloys, and magnetic materials. Keeping in view the importance of these metals and alloys and the expertise available in India for making them, the NCST has identified two projects for their development the setting up of a special metal and superalloys plant and the development of controlled-expansion alloys. 

Thermomechanical processing (TMP) has first been developed in the second half of the last century for decreasing the ductile to brittle transition temperature of construction steels. It has then progressively been extended to other categories of structural metallic materials, such as titanium alloys or nickel base superalloys for aircraft forged turbine parts. More recently, investigations have been carried out to assess the possibility and advantage of TMP for ferritic and austenitic stainless steels. 

Major industrial uses of tantalum include the production of electrical components (mainly capacitors), superalloys, tantalum carbide, and in the chemical industry (Cunningham 2000). Its physical properties make tantalum an important component of superalloys (produced by combination with cobalt, iron, nickel, and titanium) commonly used in the aerospace industry. In the chemical industry, tantalum s corrosion resistance is taken advantage of in the production of heat exchangers, evaporators, condensers, pumps, and liners for reactors and tanks (Cunningham 2000). The recycling of industrial and obsolete tantalum-containing scrap represents approximately 20% of the total tantalum consumption in the US (Cunningham 2000). 

Table 2. Properties of alloys based on the titanium aluminides TijAl and TiAl compared with conventional titanium alloys and nickel-base superalloys (Morral, 1980, Lipsitt, 1985a Kim, 1989 Kim and Froes, 1990 Froes et al., 1991).

Superabrasive tools, primarily PCBN, have been used to successfully weld ferritic steels, ferritic stainless steels, austenitic stainless steels, nickel-base superalloys. Invar, and Narloy-Z. Attempts to weld titanium with PCBN tools have been inconclusive. Tool life of 80 m (260 ft) has been demonstrated in FSW of 1018 steel, and very low tool wear has been reported on all other alloys. The primary concern in tool life continues to be fracture, and developments in PCBN grades continue to improve the fracture toughness of the FSW tools. The PCBN tools provide an extremely smooth finish when used for FSW or FSP. 

Austenitic stainless steel, duplex stainless steel, nickel superalloys, titanium, graphite... 

Some applications do not require a pattern etch but require an overall etch to thin the material or reduce weight in racing cars or even to taper a tall structure such as a yacht mast. These techniques are often applied to aluminum and titanium alloys, stainless steels, and even superalloys such as Rene 41 (Bellows 1977 Dini 1984). 

Sublattices B and A of the y -phase can dissolve a considerable amount of other elements. Many of the industrial nickel-based superalloys also contain, in addition to chromium, aluminum, and titanium, molybdenum, tungsten, niobium, tantalum, and cobalt. The addition of rhenium and ruthenium are under investigation for superaUoys, which must withstand high stresses at temperatures from 1273 to 1373 K. 

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