Making the grade

News and developments in the world of corrosion resistant alloys through the eyes of Corrotherm International

Heat-resistant superalloys and their applications – a guide

15 January 2019

Heat-resistant superalloys and their applications
We explore why nickel superalloys are so widely used in high-temperature environments and their typical applications

Nickel superalloys, as stocked by us here at Corrotherm, are an incredibly important group of products. They are used widely in high-temperature environments where materials must resist corrosion and retain their strength, toughness and structure. Each superalloy is manufactured carefully, balancing key compositional elements to give desirable properties for a range of industrial applications.

For example, within the aerospace industry, nickel superalloys have many essential applications. They are employed within the hottest areas of jet engines, where temperatures can regularly exceed 1200°C. Materials in this area must be able to withstand those conditions without compromising the structural integrity of the engine. Such superalloys are perfect for the job, as they are engineered to offer superior resistance against corrosion and oxidation at elevated temperatures.

Jet engine applications

When using superalloys in jet engines, it’s important to look to a nickel-based product, one with high levels of chromium, iron, titanium and cobalt. INCONEL alloy 601 is a good example of this. It has 58% nickel and 20-23% chromium, as well as all the other necessary key elements. In particular, it has the addition of aluminium, which enables the alloy to resist high-temperature oxidation and aqueous corrosion. It also has a high mechanical strength and can be readily machined and welded, making it a very versatile material for jet engine use.

The introduction of better superalloys has helped to develop the jet engine. As the materials are manufactured with increasingly better properties – such as increased high-temperature resistance and corrosion resistance – design engineers are able to make improvements to jet engine performance, including higher thrust and lower fuel consumption.

Processing chemicals and waste

Back down on the ground, there are other environments that rely on superalloys and their exceptional heat resistance. In the processing industries, these kinds of high-performance materials are integral to systems we all rely on.

Waste fluid treatment plants, for example, are necessary but difficult environments. They are highly corrosive and very hot. INCONEL alloy C-276 is known for its outstanding corrosion resistant in the most inhospitable of atmospheres. Its composition is such that it can withstand even the most severe system. It has a low carbon content, which minimises carbide precipitation during welding to help it maintain its corrosion resistance in as-welded structures, enhancing its usefulness. It also has a high level of molybdenum (15-17%), which gives the alloy strength, as well as better resistance to pitting and crevice corrosion. As well as waste treatment, this superalloy is used in pollution-control systems, chemical processing, and pulp and paper production, thanks to its unique characteristics.

Oil and gas extraction

The oil and gas industry has some incredibly corrosive, high-temperature situations to deal with. The materials used in these systems are paramount to the safe extraction of essential resources, and therefore they must be up to the job. Nickel superalloys are used for both onshore and offshore extraction projects, for everything from pumps and valves to process-control equipment.

One of the key materials used is INCONEL alloy 625, a flagship nickel alloy due to its exceptional properties. This material offers high strength, outstanding corrosion resistance and high-temperature resistance. It has a unique composition, with nickel, chromium, molybdenum and niobium, that gives it particularly superior resistance to severely corrosive environments. One of its key uses, though it has many, is in pipelines used for gathering sour gas. It’s also used in the separation of extracted fluids in the processing equipment for liquefied natural gas production.

Find out more about the heat-resistant properties of our superalloys and their various applications on our website, or contact a member of our Sales team to talk about your requirements.