High-temperature applications, nickel

Platinum is especially suitable for this application because even at high temperatures it has a good stability and a good resistance to contamination. However, different metals, all having a positive temperature coefficient, may be used, such as tungsten (for very high-temperature applications), nickel and nickel alloys and also (but rarely because of their low resistivity) gold and silver. 

Carbide-based cermets have particles of carbides of tungsten, chromium, and titanium. Tungsten carbide in a cobalt matrix is used in machine parts requiring very high hardness such as wire-drawing dies, valves, etc. Chromium carbide in a cobalt matrix has high corrosion and abrasion resistance it also has a coefficient of thermal expansion close to that of steel, so is well-suited for use in valves. Titanium carbide in either a nickel or a cobalt matrix is often used in high-temperature applications such as turbine parts. Cermets are also used as nuclear reactor fuel elements and control rods. Fuel elements can be uranium oxide particles in stainless steel ceramic, whereas boron carbide in stainless steel is used for control rods. 

Silver-palladium-manganese brazes possess excellent creep characteristics and have been developed for high-temperature applications involving the use of cobalt or nickel-based alloys, heat-resistant steels, molybdenum and tungsten. Their liquidus temperatures lie in the range 1 100-1 250°C. 

There are no significant high-temperature applications for alloys of nickel with iron. The scales formed in air consist of nickel oxide and iron oxide and the latter is usually present in the form of the spinel, NiO-FejOj . In the case of the more dilute nickel alloys, internal oxidation of nickel was Observed S. Substitution of a substantial proportion of nickel by iron results in a deterioration in the oxidation resistance of nickel-chromium... 

Temperature resistance, i.e. a combination of melting point and oxidation resistance, may be of prime importance. A general correlation exists between melting point and hardness since both reflect the bond strength of the atoms in the crystal lattice, and the preferred order of coating metals for use in high temperature applications as temperature is increased is silver, aluminium, nickel, rhenium, chromium, palladium, platinum and rhodium. 

For soldering aluminum, combinations of cadmium and zinc are widely used, the most satisfactory being the 60% Cd—40% Zn alloy, in addition to a 95% Cd—5% Ag solder. In high speed and high temperature applications, which are too severe for tin or lead bearings, SAE 18, containing 1% nickel and 99% cadmium, and SAE 180, containing 0.7% silver, 0.6% copper, and 98.7% cadmium, are employed. 

The contact ends of printed circuit boards are copper. Alloys of nickel and iron are used as substrates in hermetic connectors in which glass (qv) is the dielectric material. Terminals are fabricated from brass or copper from nickel, for high temperature applications from aluminum, when aluminum conductors are used and from steel when high strength is required. Because steel has poor corrosion resistance, it is always plated using a protective metal, such as tin (see Tin AND TIN. alloys). Other substrates can be unplated when high contact normal forces, usually more than 5 N, are available to mechanically disrupt insulating oxide films on the surfaces and thereby assure metallic contact (see Corrosion and corrosion control). 

Due to the potential high-temperature application of nanocomposites, as well as the fact that metal-reinforced ceramic nanocomposites combine metal and non-metal phases in equilibrium, it is important to understand the oxidation resistance of such materials. Using the Ni-alumina system as an example, and following Sekino et al.,12 the partial pressure of oxygen required to prevent the formation of nickel spinel (NiAl204) from a two-phase mixture of Ni and A1203 can be described as 58,59... 

To meeet the demands of high-temperature applications such as hydrocarbon steam reforming and partial oxidation reactions, nickel-based alloys are frequently taken into consideration [10]. 

Corrosion Resistance of Nickel-based Alloys. Nickel-based alloys are solid solutions based on nickel. Nickel-based alloys used for low-temperature aqueous or condensed systems are generally known as corrosion-resistant alloys (CRA), and nickel alloys used for high-temperature applications are known as heat-resistant alloys (HRA), high-temperature alloys (HTA), or superalloys. The corrosion performance could change due to the presence of second phase or a weld seam. (Rebak)5... 

Creep resistance will be important if the material is subjected to high stresses at elevated temperatures. Special alloys, such as Inconel 600 (UNS N06600) or Incoloy 800 (UNS N08800) (both trademarks of International Nickel Co.) are used for high-temperature equipment such as furnace tubes in environments that do not contain sulfur. The selection of materials for high-temperature applications is discussed by Day (1979) and Lai (1990). 

Chromium carbides are mainly utilized in cemented carbide alloys with a nickel bonding phase. The.se alloys are notable for their good corrosion and scaling resistance combined with abrasion resistance and are therefore utilized in high temperature applications. 

FIGURE 5.7 Optical micrographs of the reaction products between Ni and Al. (a) Duplex phases of nickel aluminides formed after a treatment of 1000°C for 1 hour in vacuum (b) a cracked nickel aluminide layer formed after being treated at 640°C for 1 hour in vacuum and (c) a cross-section of a nickel and zirconia joint which was joined together through a nickel aluminide layer at a temperature of 680°C in vacuum. N nickel, R nickel aluminide, A aluminium, and C zirconia. (Reprinted from Mei, J. and Xiao, R, Joining metals to zirconia for high temperature applications, Scripta Materialia 40 (1999) 587-594, with permission from Elsevier Science.)... 

Nickel based superalloys are one of three groups of materials used for demanding, high-temperature applications such as jet engines and gas turbines (e.g., Inconel X-750). The other two groups are iron-based and cobalt-based superalloys. 

Nickel alloys plus nickel are widely used for services, including acids, caustics, corrosive waters, and for numerous corrosive process applications and low- and high-temperature applications. For further information contact ... 

Since many years the intermetallic phases based on aluminides have been an important topic for research and development, because of their high melting points, low densities and excelent corrosion resistance at high temperatures. Especially, nickel aluminides have been of great interest as coating materials for several high temperature applications. 

Aluminides based on the intermetallic phases Ni3Al and Fe3Al are considered both as structural materials and as coatings for high temperature applications [1-6]. Their excellent corrosion resistance is due to their forming a dense, protective alumina scale. Alumina, especially ot-Al203, shows low rate constants even at temperatures above 1000°C [7]. Unlike chromia, which is formed on conventional stainless steels and nickel base alloys, alumina does not evaporate above 1000°C [8] and it is even stable in oxygen deficient atmospheres. 

New structural intermetallic alloys for high-temperature applications are at the center of the present interest in intermetallics, which is still growing. A few developments, which are based on the classic phases NijAl, TijAl and TiAl, and which are known as the nickel aluminides and the titanium aluminides, are on the brink of commercialization, but even these developments are still at an early stage compared with other developments of advanced materials, e.g. the modern engineering ceramics. Much more experimental and theoretical work is necessary to solve the processing problems and to ad-... 

Halogenated polyesters are widely used in the pulp and paper industry in bleach atmospheres where they outperform stainless steel and high-nickel alloys. Applications are also found for ductwork, fans, and other areas where potential fire hazards may be present. They are also used for high-temperature applications such as chimney liners, chemical storage tanks, and chemical piping among other applications. 

Similar studies on nickel-coated polyetherimide indicated that only the first two regions were present. Thermal deterioration of the nickel/polymer bond, region C, was not observed after 3000 hrs at 175 C. This indicates that nickel is superior to copper for prolonged high temperature applications. 

EFFECT OF PROCESSING CONDITIONS ON STRUCTURE, PROPERTIES AND PERFORMANCE OF A NICKEL BASE CAST SUPERALLOY FOR HIGH TEMPERATURE APPLICATIONS... 

Effect of Processing Conditions on Structure, Properties and Performance of a Nickel Base Cast Superalloy for High Temperature Applications..357... 

Iron-, nickel-, and cobalt-based alloys used primarily for high-temperature applications are known as superalloys. The iron-based grades, which are less expensive than cobalt- or nickel-based grades, are of three types ... 

This service test method covers procedures for the identification and measurement of the extent of carburization in a metal sample and for the interpretation and evaluation of the effects of carburization. It applies mainly to iron- and nickel-based alloys for high-temperature applications. Four methods are described ... 

World consumption of tantalum was about 2000 tonnes in 2001. Tantalum, like niobium, is used in superalloys based on nickel and cobalt, intended for aircraft engines and other high-temperature applications. Tantalum carbide TaC is, to a limited extent, used as a hard component in cemented carbide. The oxide is used to make special glass with a high refractive index for camera lenses Two tantalum properties have, however, given the metal its special importance in modern industry. 

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