Characteristics of Nickel Alloys

What makes a nickel alloy?
Obviously, the common ingredient in all nickel alloys is … nickel. This durable metal brings to the mix exceptional corrosion, oxidation and temperature resistance combined with a high degree of ductility and formability. It's no wonder that nickel alloys are a stalwart choice across a range of industries and sectors. In fact, it's estimated that year to year, 90% of all nickel sold is purchased especially to make alloys.

Nickel alloys can be made in a variety of different compositions, each providing its own unique benefits. They make materials lighter, longer lasting, corrosion resistant, and strong enough for the toughest applications.

Nickel and nickel alloys are non-ferrous metals with high strength and toughness, excellent corrosion resistance, and superior elevated temperature properties. Products differ in terms of composition, grade, shape, dimensions, and features. Commercially pure, unalloyed, or very low alloy nickel does not contain or contains only very small amounts of alloying elements. By contrast, nickel alloys contain significant amounts of added elements or constituents. Clad or bimetal stock consists of two different alloys that are bonded integrally together. Metal matrix composites have a composite or reinforced metal or alloy matrix filled with a second component, which may be in particulate, chopped fiber, continuous filament, or fabric form. Other unlisted, specialty or proprietary nickel and nickel alloys are also available. These materials are often based on a unique alloy system, use a novel processing technology, or have properties tailored for specific applications.

Many nickel and nickel alloys meet the compositional standards of the Unified Numbering System (UNS), a specification established by the American Society for Testing and Materials (ASTM), the Society of Automotive Engineers (SAE), and metal trade associations such as the American Iron and Steel Institute (AISI). The UNS assigns metals and alloys a lettered prefix and a five-digit number. Nickel and nickel alloys belong to the UNS N category and have designations such as UNS N02200. Other standards for nickel and nickel alloys include casting grades, European Norm (EN), American Society of Mechanical Engineers (ASME) standards, and U.S. military specifications (MIL-SPEC). QQ and QQS prefixes are used to designate specific MIL-SPEC metals.

Selecting nickel and nickel alloys requires an analysis of dimensions, production processes, and performance features. Outer diameter (OD), inner diameter (ID), overall length, and overall thickness are important dimensions. Most materials are cast, wrought, extruded, forged, cold-finished, hot-rolled, or formed by compacting powdered metals or alloys. Performance features for nickel and nickel alloys include resistance to corrosion, heat, and wear.

Nickel is well-known as an essential alloying element in stainless steels, Ni-Cu alloys, Ni-Fe alloys, Ni-Cr-Fe alloys, super alloys, as nickel-chromium alloys and special corrosion-resistant and high temperature alloys. Nickel ferromagnetic with a density of 8.9 g/cm3. It is ductile and malleable like steel. Nickel alloys are well-known for their high temperature strength and good resistance to corrosion.
Classification of Nickel Alloys
The nickel alloys can be classified in the following groups on the basis of their chemical compositions:
(1)Nickel
Pure nickel (99.56%)
Commercially pure nickel (wrought) 99.6–99.7%.
(2)Nickel and copper
Low nickel alloys (2–13% Ni)
Cupronickel (10–30% Ni)
Non-magnetic alloys (~60% Ni)
High nickel alloys (over 50% Ni)
(3)Nickel and iron
Wrought alloys steels (0.5–9% Ni)
Cast alloy steels (0.5–0.9% Ni)
Alloy cast iron (1–6, 14–36% Ni)
(4)Iron-nickel and chromium alloys
Stainless steels (2–25% Ni)
Maraging steels (18% Ni)
(5)Nickel-chromium-molybdenum and iron-nickel base precipitation hardened alloys.