Nickel and Nickel Alloys Information
Nickel and nickel alloys are non-ferrous metals with high strength and toughness, excellent corrosion resistance, and superior elevated temperature properties. Pure nickel is a bright silver-white metallic element of the iron group and is hard, malleable, and ductile. Pure nickel itself is tough and corrosion resistant and provides an excellent base for developing specialized alloys.
There are three common types of nickel-based alloys which are formed for different applications.
Nickel chromium alloys are designed to resist failure from both oxidation and loss of strength at high temperatures. In some applications, where conditions are less demanding, some nickel is replaced with iron to decrease costs. Nickel alloys are not suitable for high temperature sulfur rich environments such as coal-burning plants. Other metals like molybdenum, iron, and aluminum are added in specific amounts for specialized applications.
Nickel copper alloys are particularly useful when magnetic permeability may be an issue. Although the introduction of copper results in lower tensile strength and ductility, the lack of magnetic properties make them an excellent choice for oncology systems, shielding electrical sensors in applications such as well logging, or rotating inertia members used near guidance systems.
Nickel iron alloys are used for controlled expansion since the combined thermal expansion coefficient of iron and nickel is relatively low and constant over a large range of temperatures. They are used in applications where mechanical properties must remain constant with temperature changes, such as in precision springs or glass seals.
Selecting metal alloys requires an analysis of the desired dimensions and specifications. Dimensions to consider include:
- Outer diameter (OD)
- Inner diameter (ID)
- Overall length
- Overall thickness
Other specifications of importance (based on application) include product shape, tensile strength, yield strength, melting point, conductivity, corrosion resistance, ductility, and malleability. These properties differ based on the forming method and alloy composition.
Nickel and nickel alloys are able to withstand an assortment of extreme operating conditions involving environments that are corrosive, high temperature, high stress, and combinations of these factors. They are used in aircraft gas turbines, steam turbine power plants, medical applications, nuclear power systems, and the chemical and petrochemical industries. Specialized applications include low-expansion, electrical resistance, and shape memory.