Nickel is a versatile metal that is found in abundance in the earth’s crust and core. First discovered and isolated by Axel Fredrik Cronstedt, a Swedish chemist and mineralogist, nickel exhibits several desirable properties that render it useful in industrial applications. For one, nickel is highly ductile and is valuable as an alloying element to alter the properties of other metals. For example, grades of stainless steel can be created by the addition of nickel to produce alloys that offer corrosion resistance and high-temperature endurance, making them ideal for uses in chemical plants where exposure to caustic substances may be expected.
This article will focus on reviewing the different types of nickel alloys that are commonly available. The alloy definition in the case of nickel alloys is one in which nickel is the primary element (i.e. has the highest concentration of all the metals in the alloy).
Properties of Nickel
Nickel, whose chemical symbol is Ni, has a silvery-white appearance and is a primordial element, with a face-centered cubic crystalline structure. It is magnetic at room temperature and has a Curie temperature of 253oC (487oF). Table 1 below summarizes some of the other key physical properties and characteristics of nickel.
Table 1 – Characteristics and Properties of Nickel (Ni)
Characteristic
Value
Atomic number
28
Atomic weight
58.69
Melting point
1453oC
Boiling Point
2730oC
Recyclable/Recoverable
Yes
Density
8.90 g/cm3 @ 25oC
Curie Temperature
253oC
Sound transmissibility
4,900 m/s @ room temperature
Coefficient of Thermal Expansion
13.4 μm/(m-oK)
Coefficient of Thermal Conductivity
90.9 W/(m-oK)
Electrical Resistivity
69.3 nΩ-m @20oC
Young’s Modulus
200 GPa
Bulk Modulus
180 GPa
Shear modulus
76 GPa
Poisson’s ratio
0.31
Mohs hardness
4.0
Vickers hardness
638 MPa
Common Types of Nickel Alloys
Nickel will alloy easily with most metals such as copper, chromium, iron, and molybdenum. The addition of nickel to other metals alters the properties of the resulting alloy and can be used to produce desired characteristics such as improved corrosion or oxidation resistance, increased high-temperature performance, or lower coefficients of thermal expansion, for example.
The sections below present information about each of these types of nickel alloys.
Nickel-Iron Alloys
Nickel-iron alloys function in applications where the desired property is a low rate of thermal expansion. Invar 36®, also sold with trade names of Nilo 6® or Pernifer 6®, exhibits a coefficient of thermal expansion that is about 1/10 that of carbon steel. This high degree of dimensional stability renders nickel-iron alloys useful in applications such as precision measurement equipment or thermostat rods. Other nickel-iron alloys with even greater concentrations of nickel are used in applications where soft magnetic properties are important, such as transformers, inductors, or memory storage devices.
Nickel-Copper Alloys
Nickel-copper alloys are very resistant to corrosion by salt water or seawater and thus find application in marine applications. As an example, Monel 400®, also sold under the trade names Nickelvac® 400 or Nicorros® 400, can find application in marine piping systems, pump shafts, and seawater valves. This alloy as a minimum concentration of 63% nickel and 28-34% copper.
Nickel-Molybdenum Alloys
Nickel-molybdenum alloys offer high chemical resistance to strong acids and other reducers such as hydrochloric acid, hydrogen chloride, sulfuric acid, and phosphoric acid. The chemical makeup for an alloy of this type, such as Alloy B-2®, has a concentration of molybdenum of 29-30% and a nickel concentration of between 66-74%. Applications include pumps and valves, gaskets, pressure vessels, heat exchangers, and piping products.
Nickel-Chromium Alloys
Nickel-chromium alloys are prized for their high corrosion resistance, high-temperature strength, and high electrical resistance. For example, the alloy NiCr 70/30, also designated as Ni70Cr30, Nikrothal 70, Resistohm 70, and X30H70 has a melting point of 1380oC and an electrical resistivity of 1.18 μΩ-m. Heating elements such as in toasters and other electrical resistance heaters make use of nickel-chromium alloys. When produced in wire form they are known as Nichrome® wire.
Nickel-Chromium-Iron Alloys
Nickel-chromium-iron alloys combine these elements to produce alloys that resist oxidation and high-temperature corrosion. Alloy 800, sold under the trade names Incoloy 800®, Ferrochronin® 800, Nickelvac® 800, and Nicrofer® 3220, is used in furnace components such as petrochemical furnace cracker tubes, and as a material for sheathing of electrical heating elements. These alloys generally are also valued for their optimum creep and rupture properties at high temperatures. The composition of these alloys is typically 30-35% Nickel, 19-23% Chromium and a minimum of 39.5% Iron. The high concentration of iron has led to the reclassification of these alloys as stainless steel.
Nickel-Chromium-Molybdenum Alloys
With similar applications to nickel-molybdenum alloys, nickel-chromium-molybdenum alloys also provide high corrosion resistance especially with regard to reducing acids such as hydrochloric acid and sulfuric acid. One of the best known of these alloys is Alloy C-276, also sold under the trade names Hastelloy C276®, Nickelvac® HC-276, Inconel® 276, and Nicrofer® 5716. This alloy is used in pollution control stack liners, ducts, and scrubbers, as well as in chemical processing components such as heat exchangers, evaporators, or reaction vessels. The composition of this alloy is primarily nickel with 15-17% molybdenum, 14.5-16.5% chromium, 4-7% Iron, 3-4.5% tungsten, and smaller concentrations of other elements such as manganese.
Nickel-Chromium-Cobalt Alloys
These alloys of nickel add chromium and molybdenum to add creep rupture strength to the alloy. Alloy 617 is an example, sold under the trade names Inconel 617® and Nicrofer® 617, which has a composition of 20-24% chromium, 10-15% cobalt, and 8-10% molybdenum with a minimum nickel content of 44.5%. Applications for these alloys include industrial furnace components, gas turbines, catalyst grid supports to produce nitric acid, and fossil fuel production facilities.
Nickel-Titanium Alloys
Nickel-titanium alloys feature shape retention of shape memory properties. By forming a shape from this alloy at a higher temperature and them deforming it from that formed shape at a lower temperature, the alloy will remember the initial shape and reform to that shape once heated to this so-called transition temperature. By controlling the composition of the alloy, the transition temperature can be altered. These alloys have a super-elastic property that can be exploited to provide, among other uses, a shock absorber against earthquake damage to help protect stone buildings.
Nickel Alloy Form Factors
Suppliers of nickel alloys offer them in a variety of form factors which commonly include:
Angles
Balls
Pipe
Tubing
Bars
Billets
Ingots
Channels
Coils
Wire
Rods
Sheets
Plate
Strips
Flanges
Forgings
Pipe fittings
Other material form options such as forged rings, billets, or blocks may be available from suppliers as needed by quote.
Common Nickel Alloy Trade Names
Below in Table 2 are some of the more common trade names of the types of nickel alloys sold in the marketplace.
Table 2 – Common Nickel Alloy Types and Trade Names
Name Alloy type Alternative trade names
Nickel 200 99% + pure Nickel Nickel 99.2
Nickel 201 99% + pure Nickel Nickel 201, LC Nickel 99.2
Monel 400® Nickel-Copper Nickelvac® 400, Nicorros® 400
Monel R405® Nickel-Copper
Monel K500® Nickel-Copper
Inconel 600® Nickel-Chromium-Iron Nickelvac® 600, Ferrochronin® 600
Inconel 601® Nickel-Chromium-Iron Pyromet® 601, Nicrofer® 601
Inconel 617® Nickel-Chromium-Cobalt Nicrofer® 617
Inconel 625® Nickel-Chromium-Iron Chornin® 625, Altemp® 625, Nickelvac® 625, Haynes® 625 Nicrofer® 6020
Inconel 718® Nickel-Chromium-Iron Nicrofer® 5219, Alvac® 718, Haynes® 718, Altemp® 718
Inconel X750® Nickel-Chromium-Iron Haynes X750®, Pyromet® X750, Nickelvac®X750, Nicorros® 7016
Incoloy 800® Nickel-Chromium-Iron Ferrochronin® 800, Nickelvac® 800, Nicrofer® 3220
Incoloy 825® Nickel-Chromium-Iron Nickelvac® 825, Nicrofer 4241®
Hastelloy C22® Chromium-Molybdenum-Tungsten Inconel® 22, Nicrofer® 5621
Hastelloy C276® Nickel-Chromium-Molybdenum Nickelvac® HC-276, Inconel® 276, Nicrofer® 5716
Hastelloy B2® Nickel-Chromium-Molybdenum Nimofer® 6928
Hastelloy X® Nickel-Chromium-Iron-Molybdenum Nickelvac® HX, Nicrofer® 4722, Altemp® HX, Inconel® HX
Vascomax® C250 Nickel-Cobalt-Molybdenum Maraging C250™, Maraging 250™
Vascomax® 300 Nickel-Cobalt-Molybdenum Maraging 300, Maraging C300®, and Vascomax® C300
Vascomax® C350 Nickel-Cobalt-Steel Maraging C350™
Rene® 41 Nickel-Chromium
Multimet® N155 Nickel-Chromium-Cobalt
Waspaloy 25™ Nickel-Cobalt
Invar 36® Nickel-Iron Nilo 6®, Pernifer 6®
Invar 42® Nickel-Iron Nilo 42®
Summary
This article provided a brief review of the more common types of nickel alloys and their uses. For information on other products.
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