History of discovery of nickel alloys. Physical and mechanical properties.

Nickel has the property of dissolving other metals without losing its merits, giving alloys heat resistance and ductility. This property has given rise to a large number of nickel alloys, which have a number of advantages. Nickel forms solid solutions with other metals, which have ferromagnetism and high corrosion resistance in gas and liquid aggressive environments. In these alloys there are no allotropic transformations.

Since the end of the 19th century nickel-copper alloys with high ductility, valuable electrical properties and corrosion resistance have become increasingly popular. Monel-type alloys found the widest practical application. Such alloys together with cunyals stand out among structural materials by high chemical resistance in water, gas environments, in strong alkalis and acids.

Ferromagnetic alloys (40-85% Ni + Fe) play an important role in technology. These alloys belong to the class of magnetically soft materials. Among them there are alloys that are characterized by high value of magnetic permeability - permalloy; constancy, qualities under changing external conditions - perminvar; high magnetic permeability and maximum magnetic saturation - permenorm. Such alloys are widely used in almost all areas of technology, where there is a need for high sensitivity of working elements to fluctuations in the magnetic field.

Alloys with 45-55% Ni are in demand in sealed contacts between glass and metal. Such alloys alloyed with Co or Cu have practically the same coefficient of linear thermal expansion with glass.

Ni + Co alloys that have 4 or 18% nickel are classified as magnetostrictive materials. Such alloys have high corrosion resistance in sea and river water. As a rule, they are widely used for the manufacture of hydroacoustic equipment.

With the advent of the twentieth century and the development of electrical engineering a new class of nickel alloys was developed. The heat resistance of this metal in air is very high, but it can be improved by Cr, Si, Al. Nickel alloys with Si Al, Mn and Ni alloys with 10% Cr have heat resistance combined with thermoelectric properties. The most common thermocouples are chromel-alumel thermocouples and are used in laboratory and industrial applications. Copel and chromel thermocouples are also used.

Ni c Cr alloys, also called nichromes. These alloys are heat resistant and are widely used in engineering. Still, nichromes with a nickel content of about 80% are especially popular. They were considered the most heat-resistant industrial alloys, but only until the advent of chromals. In order to make nichromes cheaper, the nickel content was reduced, and so ferronichromes were born. In ferronichromes, most of the nickel is replaced by iron. The most common composition contains 60% Ni, 15% Cr, 25% Fe.

Compared to nichromes ferronichromes have a lower operating resistance and are used at lower temperatures. It is worth noting that both nichromes and ferronichromes have a very high electrical resistance of approximately 1.05-1.4 μOhm-m2/m. Together with chromals they are part of the most important classes of alloys that are used to make high-temperature electric heaters. As a rule, nichromes that are alloyed with silicon, up to about 1.5%, are used together with metals such as rare-earth and alkaline-earth metals. The operating temperature limit for this type of nichrome is 1200 °C, and for some grades up to 1250 °C. Nichromes are competed by heat-resistant alloys that contain 15-30% Cr and up to 4% Al. Alloys alloyed with Si are not so heat-resistant. But from chromium-containing alloys, alloyed with aluminum, it is much more difficult to obtain a homogeneous composition of the strip or wire for the reliable operation of electric heaters was. Because of this, such alloys are mainly used in the manufacture of heat-resistant parts with a permissible operating temperature of up to 1250 °C that are not subject to heavy mechanical loads.

During World War 2 in Great Britain they began to produce nimonics - heat-resistant alloys Ni - Cr - Ti - Al. These alloys are particularly strong due to the alloying of chromium with 2.5% titanium and 1.2% aluminium. These alloys are superior to nichrome and alloy steels in heat resistance. Prior to that, steels were used that were workable up to t° 750-800°C. Appearance of nimonics opened the era of aircraft gas turbine engines. In a short period of time, a large number of complex alloys were created which belong to nimonics. These are alloys with Ti, Al, Nb, Ce, La, B, Zr. Their operating temperature reaches 1000 ° C. ... The quality of the alloys is adversely affected by complex alloying - the ability of the alloys to hot work with pressure is impaired. It should be noted that wrought and alloyed cast alloys, gained their recognition precisely because of their high heat resistance. But at the same time cast alloys are not completely homogeneous in structure, due to which there is a scattering of properties. To find the optimal composition, refractory oxides of thorium, zirconium, and aluminum and other compounds were introduced into the alloys. The best was a nickel alloy with highly dispersed thorium oxides.

Alloys Ni - Mn, Ni - Cr, Ni - Mo play a very important role in technology. These alloys have valuable electrical properties: high electrical resistance, low value of thermal expansion coefficient, and paired with copper have a small value of thermal EMF. These alloys are inferior to manganin in the value of the coefficient of thermal electrical resistance in the range of room temperatures, but have 3-4 times greater specific electrical resistance. Such alloys are used for small-sized resistive elements, where constant electrical properties throughout the service life are required. These elements are made of thin foil or microwire with a thickness of 5 to 20 microns. Ni - Cr or Ni - Mo alloys are used to manufacture small strain gauges. In such alloys there is a linear dependence of the change in electrical resistance on the value of the elastic deformation.

Chemical equipment often works in corrosive environments of sulfuric, hydrochloric and phosphoric acids of different concentrations at temperatures that are as close to the boiling point as possible. Alloys Ni - Cr - Mo, Ni - Mo abroad are known as halsteloy and remanite. In USSR these alloys are known under the brand names H70M28, Kh15N65M16V, H70M28F, Kh15N55M16V. These alloys surpass all known steels in corrosion resistance.

In practice, many more nickel alloys with Fe, and Mo, and Cr, as well as other elements that have the right combination of mechanical and physical-chemical properties. Thus, corrosion-resistant alloys for springs and hard alloys for stamps, as well as many others are produced. In addition to these alloys, nickel is a component of other metals.

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