Alloys of iron and nickel have a wide variety of uses. Their excellent corrosion resistance makes them particularly popular when combined with chromium and molybdenum alloys. An exceptionally fantastic fact about Cobalt Alloys.
Arnold PTM provides a selection of nickel-iron alloys, such as Invar 36 and soft magnetic alloys. These alloys feature low thermal expansion rates and are often found in precision measurement equipment and thermostat rods.
High-permeability alloys
Arnold PTM provides a selection of these nickel-iron alloys with high permeability for transformers, motors, and relays as they convert electrical energy to mechanical force. Their high permeability converts electrical energy to mechanical power more effectively. Arnold PTM offers free-machining versions to facilitate component fabrication.
The highest permeability alloys tend to contain higher nickel concentrations. One such alloy, JLC TC alloy, was designed with square loop behavior in mind to absorb energy more effectively at lower magnetizing forces than its peers in this family of nickel irons. With high initial and maximum permeabilities, low core loss, and good cold-formability properties – it’s perfect for use as cores in power supply transformers, servo-synchros, and other control devices operating either DC or AC frequencies.
Other grades within the high-permeability alloy family feature lower nickel contents; for instance, 77 Alloy has become popular as it provides corrosion resistance and has also been utilized by electrical devices requiring high permeability at meager magnetizing forces.
Permalloy, a nickel-iron-molybdenum alloy, is another high-permeability material with significant advantages such as low coercivity and very little magnetostriction, which reduce stress on magnetic properties at various stress levels. Unfortunately, it is usually reserved for more complex shapes requiring other high-permeability materials due to not being very ductile or workable.
Basic electrical irons are electric arc melted and processed to achieve soft magnetic properties, usually by annealing in an oxygen-free hydrogen atmosphere at 2150degF (1177degC). After being annealed, they can be rolled into various shapes for magnetic shielding purposes or used to fabricate laminated cores for transformers, relays, or tape toroids.
Vanadium adds another level of permeability and low core losses to basic electrical irons, producing alloys such as JLC Alloy 50A and SMA 50A with vanadium, which have excellent magnetic saturation of 24 kilogauss at relatively low coercive forces; they also exhibit shallow hysteresis losses.
Low-temperature alloys
Nickel alloys incredibly well with other metals, particularly iron. This enables it to form a wide array of alloys that are helpful in different environments and offer specific properties like resistance to corrosion, tensile strength, and high-temperature tolerance.
Low-temperature nickel alloys are widely used as fusible alloys in fuses, thermostats, switches, barometers, and electrical and thermal management products. Their characteristics include good conductivity, easy reflow, and controlled dimensional properties – with lower melting points than other nickel-iron alloys and minimal carbon uptake rates.
They exhibit excellent ductility and malleability as well as being resistant to corrosion, high-temperature scaling, strength at temperature ranges of -100 degC up to +200 degC, and linear expansion at various temperature conditions, making them suitable for chemical processing equipment like pipes, tanks, and mixing devices.
Some low-temperature nickel alloys are fortified with chromium and molybdenum to increase corrosion resistance, while other alloys like Invar 36 (also known as Nilo 6, Waspaloy 25, and Nimonic) feature higher concentrations of nickel to facilitate applications requiring lower rates of expansion.
Alloys that exhibit a low-temperature coefficient of expansion can be particularly advantageous for applications like glass-to-metal seals and soft magnetic materials, including those made up of nickel, tungsten, tin, aluminum, and molybdenum alloys.
Alloys with low-temperature expansion coefficients typically feature high permeability and muscular tensile strength, making them suitable for manufacturing components with complex shapes in cold environments. Furthermore, their resistance to stress makes them perfect for applications requiring such environments.
Nickel and iron are among the heaviest elements produced during nucleosynthesis in massive stars and can be found in telluric planets such as Earth and meteorites. Their elements combine naturally in meteorites or terrestrial metal deposits to form various naturally-occurring alloys; additionally, they can also be produced via steel metallurgy processes to produce maraging steels with low alloy content or combined with titanium to create high-temperature superalloys.
Soft magnetic alloys
Soft magnetic alloys are distinguished by their ease of magnetization (high permeability) and demagnetization, making them suitable for applications such as transformers and electric motors, where their magnetized coils can increase current flow speed while decreasing eddy recent losses. When selecting an appropriate soft magnetic alloy, it’s essential to consider its permeability, Curie temperature, hysteresis loss, iron losses, corrosion resistance, and magnetic properties at various temperatures.
Nickel-iron alloys are the best soft magnetic materials, offering higher permeabilities than silicon-iron alloys and better resistance against alkaline solutions, non-oxidizing salts, and seawater corrosion. Furthermore, many also exhibit lower thermal expansion rates, making them suitable for cryogenic temperatures – and Invar is particularly prized due to its low thermal expansion rates and superior dimensional stability, making it ideal for precision measuring instruments or thermostat rods.
Nickel-based alloys boast outstanding magnetic properties and exceptional strength and flexibility, which can be further improved through cold working or stress relief. This process creates fine-grained microstructures resistant to cracking and increases hardenability while decreasing internal stress-induced failure risk.
Innovative powder technologies are being employed to produce new soft magnetic alloys with reduced losses at high frequencies, particularly those designed specifically for magnet applications. Different concepts may be pursued depending on specific application needs – for magnets, for instance, isotropy may be achieved by casting or pressing an alloy with pressures of up to 800 MPa into desired shapes.
In many instances, alloy selection depends on several factors, including mill processing and chemical composition. Carpenter has developed a selection matrix that correlates alloys’ relative permeability and flux density with costs based on long-term experience and is also illustrated by Figure 1. Carpenter offers this selection matrix to make the selection process easier for designers, which may assist.
High-temperature alloys
High-temperature alloys are combinations of metals designed to withstand extreme temperature variations and harsh environments, including corrosion. They find extensive use in aerospace, electronics, energy, and chemical processing industries where reliability is paramount for optimal performance. Furthermore, these alloys are integral to gas turbine engines operating under high temperatures and pressures.
These alloys can be divided into four groups based on their matrix compositions. Nickel is the cornerstone for all these alloys; additional notable elements include chromium, molybdenum, aluminum, cobalt titanium, and vanadium. Also referred to as superalloys because of their exceptional strength and corrosion resistance at very high temperatures – making them suitable for even the harshest environments.
Iron-nickel base alloys such as AMS 5700 and Hastelloy X offer outstanding capabilities in temperatures ranging between 500degF (260degC) and 1000degF (543degC). Both age hardenable and non-age hardenable grades are available, though age hardenable grades tend to perform better for applications at these high temperatures due to not overtempering in this temperature range.
These materials boast exceptional oxidation resistance and resistance to reducing and nitriding environments, along with outstanding creep rupture strength and formability, making them well-suited to various applications such as instrument probes, furnace muffles, and electronic equipment.
Chromium-nickel alloys such as Hastelloy C276 and UNS N08810 are among the most frequently utilized alloys of this group, offering superior resistance to temperatures up to 2200 degF (1150degC), uniform attack, localized corrosion, stress corrosion cracking resistance, as well as stress corrosion cracking resistance. Furthermore, they are an excellent choice for chemical processing equipment, nuclear steam generator tubing systems, heat treating machinery, and food processing machines.
Nickel and chromium alloys are often specified for severe service conditions. They’re frequently employed in power generation, oil and gas, aerospace, and nuclear industries where operating at elevated temperatures is critical.
Monocrystal or single-crystal alloys are among the most advanced high-temperature alloys, featuring optimally directionally solidified structures with no grain boundaries. These metals possess extraordinary levels of strength that exceed regular steel, along with excellent ductility, weldability, and workability, making them well-suited to highly corrosive environments like gas turbines and industrial processes.
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