Fastener Materials Types of Nickel Alloys and Their Properties

Nickel readily alloys with many other metals, including chromium, iron, molybdenum, and copper. This allows for a wide variety of alloys that exhibit excellent corrosion and high-temperature scaling resistance, excellent high-temperature strength, and other unique properties.

Pure Nickel: Pure nickel UNS N02200 is used in the chemical industry for its corrosion resistance - especially to alkali metals. It is also used for its properties in shielding electromagnetic interference and transducers.

Nickel-Iron Alloys: They are used as soft magnetic materials, glass-to-metal seals, and materials with specific thermal expansion properties. Invar® (UNS K93600), which contains 36% nickel and the rest iron, is unique in that its coefficient of thermal expansion is almost zero near room temperature. This makes it valuable where high dimensional stability is required, such as precision measuring instruments and thermostat rods. It can also be used at cryogenic temperatures due to its very low thermal expansion rate. Alloys containing 72-83% nickel have the best soft magnetic properties and are used in transformers, inductors, magnetic amplifiers, magnetic shielding, and memory storage devices.

Nickel-copper alloys: They are highly resistant to corrosion from alkaline solutions, non-oxidizing salts and seawater. The best known is alloy monel 400.

Nickel-molybdenum alloys: They are highly resistant to reducing acids in the absence of oxidizing ions (such as iron and copper or dissolved oxygen). The best known is alloy B-2.

Nickel-chromium alloys: They are characterized by high corrosion resistance (anti-scaling) at both normal and high temperatures, good high-temperature strength and high electrical resistance. The alloys are mainly divided into three categories: 1. Ni-Cr (and Ni-Cr-Fe) alloys with high electrical resistance for heating elements, such as 70-30 (UNS N06008) and Grade C (UNS N06004) 2. Ni-Cr alloys (containing alloying elements such as Fe) have good corrosion resistance. The most famous are Alloy 600 (UNS N06600) and Alloy 601 (UNS N06601)3. Nickel-chromium alloys with high temperature strength and creep resistance, most of which are age-hardenable, such as Alloy X-750 (UNS N07750)

Nickel-chromium-iron alloys:

There are basically two groups of alloys:

1) Ni-Cr-Fe alloys, which have excellent high temperature strength and resistance to oxidation, carburization, and other types of high temperature corrosion. The most famous are Alloy 800 (UNS N08800) and its variants 800H (UNS N08810) and 800HT (UNS N08811). (Recently, these alloys have been classified as stainless steels, reflecting their high Fe content)

2) Ni – Cr – Fe (with Mo and Cu) alloys, which have excellent corrosion resistance in specific applications. The most famous is probably Alloy 825 (UNS N08825), which has excellent resistance to sulfuric acid. Alloy G-3 (UNS N06985) has excellent corrosion resistance to commercial phosphoric acid as well as many complex solutions containing highly oxidizing acids.

Nickel-Chromium-Molybdenum Alloys: These have high corrosion resistance, with the best known being Alloy C-276 (N10276). They have excellent resistance to reducing acids such as hydrochloric and sulfuric acids. There are a number of variations based on this composition that vary the Cr and Mo content and, in some cases, add Cu or W to extend corrosion resistance to more oxidizing or reducing conditions. These include Alloy C-22 (N06022), Alloy 59 (N08059), Alloy C-2000 (UNS N06200), and Alloy 686 (N06686).

Nickel-Chromium-Cobalt Alloys: The addition of cobalt and molybdenum gives Alloy 617 (UNS N06617) solid solution strengthening and a high level of creep rupture strength. The addition of cobalt to HR-160 (N12160) provides excellent resistance to various forms of high temperature corrosive attack, such as sulfidation and chloride attack in both reducing and oxidizing atmospheres.

Nickel-titanium alloy: Nickel-titanium alloy 55% (UNS N01555), also known as Nitinol, has shape memory properties. When formed at one temperature and then deformed at a lower temperature, it returns to its original shape when reheated. The transformation temperature can be tuned by carefully controlling the composition. Medical devices and specialized connectors are two specific applications. The same alloy can also undergo considerable elastic deformation and still return to its original shape (superelasticity). This property has been exploited for applications such as eyeglass frames and shock absorbers, which provide earthquake resistance in historic stone buildings.