There are many types of nickel alloys, but what they all have in common is a special set of properties. This makes them ideal for critical components and applications that must function in harsh environments where other materials quickly degrade or fail. They are resistant to corrosion by a wide range of media, including acids and alkalis, and they are extremely strong even at high temperatures.
Nickel also alloys well with other metals, such as chromium, cobalt, molybdenum and iron. The addition of these elements alters the properties of the alloy and can produce characteristics such as improved corrosion or oxidation resistance, higher strength at elevated temperatures, or lower coefficients of thermal expansion. For example, nickel-chromium-iron alloys such as Hastelloy(r) are extremely resistant to degradation in the presence of acidic compounds and aqueous salt solutions. They are especially suited for use in the chemical industry, such as in reactor pressure vessels and turbine blades.
The most common nickel alloys are copper-nickel, chromium-nickel and nickel molybdenum. The first of these, often referred to simply as cupronickel(r), is highly corrosion resistant and maintains its tensile strength at extreme temperatures. It is also able to operate at cryogenic temperatures. The second, nickel-chromium-nickel is very useful for use in demanding chemical processing environments, as it resists failure from both oxidation and erosion. The third, nickel-molybdenum-iron alloys such as Invar(r) have a low coefficient of thermal expansion and are particularly useful for applications that require dimensional stability. These include glass-to-metal seals and transformers.
