Investment casting nickel-base superalloys for corrosion resistance

Published - 27th Sep 2024

Investacast offers a cost-effective solution for performance critical components

Nickel-base superalloys offer excellent corrosion resistance. Components can be air cast, vacuum cast, forged or machined. In this blog we discuss why air investment casting is the optimal solution for nickel-base superalloy components required for corrosion resistance.

Investacast delivers the benefit of superior durability of nickel-base superalloy components, without the high cost.

Nickel-base superalloys in corrosive environments

Nickel-base superalloys have an exceptional ability to resist corrosion damage caused by oxidation and other chemical reactions.

Corrosion resistance is vital in many sectors where anything from seawater to corrosive chemicals will reduce the efficiency or safety of the component.

What causes corrosion in metal components?

Corrosion occurs when metal is lost due to a reaction with the environment. Corrosion can develop in the presence of liquids or gases, and may occur at any temperature, although generally the rate of corrosion increases with increasing temperature.

Components that corrode suffer from defects in their surface finish, meaning they can no longer function efficiently. If even a small component has corroded due to its harsh environment, it may be necessary to halt operations to replace that component – incurring significant downtime.

How do nickel-base superalloys resist corrosion?

Corrosion resistance depends on the inherent ability of the metal to withstand an adverse reaction with its environment. Nickel is itself inherently less reactive than metals like iron, so is relatively stable.

Nickel-base superalloys have excellent corrosion resistance due to the addition of specific elements. Chromium and titanium, for example, react with oxygen in the air to form an impermeable layer that protects the superalloy from its corrosive environment. Other elements in nickel-base superalloys, such as molybdenum, act in the same way to protect the metal from corrosive materials such as nonoxidising acids.

The benefits of excellent corrosion resistance

High corrosion resistance is crucial in performance critical applications, such as in pumps and valves in the petrochemical industry, or aid-processing equipment in the chemical engineering sector. For this reason, superalloys such as nickel-base superalloys Hastelloy and Inconel are often specified for these environments.

Components made from nickel-base superalloys also have a significantly longer lifetime in most applications than components manufactured from other metals such as stainless steel. An investment in durable nickel-base superalloy components can save time and money in the longer term, especially where the failure of a minor component can sabotage an entire operation.

What is the disadvantage of using nickel-base superalloys?

Usually, the biggest disadvantage of manufacturing from nickel-base superalloys is the cost. This can be multiple times that of a stainless steel, because:

Nickel-base superalloys are expensive metals to source.
The manufacturing process is generally expensive. Many casting companies rely on expensive vacuums to manage the chemical reactions of nickel-base superalloys; whilst forging and machining these strong metals is also challenging.

The Investacast solution for nickel-base superalloys

Investacast has the expertise to air cast these components, a cost-effective alternative to vacuum casting, forging or machining.

Where the application requires high levels of corrosion resistance, but does not need to resist extreme temperatures, air investment casting is the optimal solution. Vacuum investment casting is necessary for components that must maintain high strength at extreme temperatures, because of the need to prevent impurities in the air from impacting on performance at high temperatures.

If there is no need for the component to perform at extreme heat, vacuum casting is disproportionately expensive. Air casting by experts preserves the exceptional room temperature strength and corrosion resistant qualities of nickel-base superalloys.

Investacast nickel-base superalloy components are the cost-effective choice for highly corrosive environments, delivering near-net shape nickel-base superalloy castings that have exceptional corrosion resistance.