Hastelloy Alloy

As technology advances and industrial processes become more sophisticated, stronger materials are in high demand. To keep up with this dynamic, manufacturing materials must evolve which is where Hastelloy comes in. Hastelloy is a member of the superalloy family, developed to transcend the limitations of normal materials.

As you read on, we will explore everything there is to know about Hastelloy. Whether you are an engineer, researcher, or simply curious about these remarkable alloys, this blog post will provide you with a comprehensive understanding of Hastelloy and its significance in modern industry.

What is Hastelloy?

Hastelloys are a unique class of high-performance alloys that have excellent corrosion resistance and high-temperature strength. 

The Hastelloy superalloy is a combination of various metallic elements. These include nickel, molybdenum, chromium, iron, and tungsten. These independent metal species can be mixed variably to achieve specific properties. 

Depending on the specific production treatment they undergo, Hastelloy is rated to withstand extremely harsh conditions Ike high temperatures, and acidic, alkaline, and corrosive media.

The name ‘Hastelloy’ is derived from the Haynes International company, which was the first to develop these alloys in the 1920s. Since then, many different types of Hastelloy have been developed, each with its unique properties and applications.

General Properties of Hastelloy

Let’s take a quick look at the general properties of the superalloy that puts it in a league of its own among other materials. Key general properties of Hastelloy include;

• Excellent resistance to corrosion in harsh chemical environments
• High-temperature strength and resistance to thermal fatigue
• Excellent resistance to oxidation and high-temperature corrosion
• Good resistance to erosion and wear
• High toughness and ductility
• Good weldability and formability
• Resistance to cracking and embrittlement

Types and Grades of Hastelloy

Hastelloy has one of the most extensive alloy variations you’ll ever come across. Let’s quickly review these grade alloys, so you’ll comprehensively understand what’s best for your project. 

Hastelloy can be broadly classified into 5 grades namely;

• Hastelloy B superalloys
• Hastelloy C superalloys
• Hastelloy G superalloys
• Hastelloy N
• Hastelloy X

Chemical Composition Summary

B-type Hastelloy

Hastelloy B is basically made up of nickel and molybdenum and they make up about 88-90% of the alloy. Other hastelloy elements are present in trace quantity shared over the 10% alloy mass.

Nickel gives the alloy the ability to withstand corrosion and oxidation. While the presence of molybdenum in high quantities makes it impervious to strong reducing agents like hydrochloric acid as well as other corrosive media such as sulfuric acid, acetic acid, and phosphoric acid.

The exact composition of Hastelloy B can vary depending on the specific manufacturer and grade. 

B-2 Hastelloy

The B-2 B grade variant typically contains 65% Nickel and 30% Molybdenum. The exact composition may vary depending on the specific manufacturer. Iron, chromium, carbon, phosphorus, sulfur, cobalt, chromium, and manganese in trace amounts (between 0.03% and 5%).

The B-2 hastelloy will serve better in extremely reducing conditions. The alloy’s high resistance is unidirectional. Meaning its high reductive media resistance makes it highly vulnerable to oxidizing agents.

B-3 Hastelloy

B-3 Hastelloy has a similar composition to B-2s. This means they also have the same vulnerability to oxidizing agents. The alloy however has greater thermal stability. You won’t have to worry about whether or not the B-3 retains its properties at high temperatures and under localized corrosion elements like in pitting corrosion.

C-type Hastelloy

Nickel, chromium, and molybdenum make up the bulk of the Hastelloy C superalloys. The superalloys are renowned for their exceptional corrosion resistance in a wide range of aggressive environments, thanks to the significant presence of chromium.

The addition of chromium optimizes the Hastelloy high temperature and anti-corrosion performance. 

C-grade Hastelloy has the most applications and uses cases in the Hastelloy family. This is in part due to their high performance and their easy formability/machinability. 

Hastelloy C-276

Hastelloy C-276 is most popular for its high use case in petrochemical applications. Nickel accounts for little over half of its mass, typically between 55 and 59%. Molybdenum and chromium make up about 21% while the remaining elements are spread in smaller quantities.

Hastelloy C-276 works well in both reducing and oxidizing corrosive environments, as well as pitting, stress cracking, and intergranular corrosion 

Hastelloy C-22

Hastelloy C-22 is another popular member of the Hastelloy C family. It contains nickel(58%), chromium(20%), molybdenum(13%), and tungsten(3.5%) as base elements.

It has excellent weldability and is often used in chemical processing equipment, such as reactors, heat exchangers, and desulfurization and piping systems.

Hastelloy C-4

The Hastelloy C-4 alloy is highly ductile and corrosive resistant. If you’re working on a project with deep drawing as a parameter, you’ll find excellent use with the alloy. It contains the highest amount of nickel(60%) in the C-grade family. 

This translates to higher corrosive strength in reducing environments. The remaining constituents include molybdenum (16%), iron(3%), chromium (18%), and cobalt(2% max). Carbon, silicon, sulfur, manganese, titanium, and others are also present, but in trace form. 

Hastelloy G

Hastelloy G comprises mainly nickel, chromium, iron, and molybdenum. 

Generally, the alloy constituents are mixed as follows; nickel (42-52%), chromium (20-22%), iron (18-21%), molybdenum (5-8%), and tungsten (1-2%).

In this family, nickel primarily functions as a balance element, enhancing the materials underlying corrosive resistance. 

It also stabilizes the high-temperature resistance imbued by the trace amount of tungsten present in the alloy mixture.

Hastelloy G exhibits excellent localized corrosion, pitting, and crevice corrosion resistance. There are two main types — the G-3 and the G-30. Both boast super high-temperature resistance. The former is more so. 

Hastelloy X

Hastelloy X also known as Alloy X or UNS N06002 is a quad metal-based Hastelloy alloy. It comprises all the parent alloy constituent metals with nickel(47.5-52%), chromium(20.5-23%), iron(17-20%), and molybdenum(8-10%) as the alloy base. 

The UNS N06002 was developed for high-performance utility in high temperatures, especially in gas turbine engines and industrial furnaces. You’ll find that it’s easy to fabricate, oxidation-resistant, and stress corrosion-resistant.

Hastelloy N

Also known as UNS N10003, the N-grade Hastelloy is the only alloy grade with over 70% nickel composition. 

The implication is that the alloy is nickel based. This gives it an edge over other members of the Hastelloy family when it comes to corrosion resistance and high-temperature performance.

The alloy comprises mainly nickel(71%), molybdenum(16%), chromium (7%), and iron(5% max).

Overall, alloy N has excellent resistance to both oxidizing and reducing environments, including wet chlorine gas, sulfuric acid, and hydrochloric acid. This makes it especially useful in aggressive chemical environments.

Mechanical Properties

Manufacturing Process

Like with every other alloy, the bulk of Hastelloy’s manufacturing process is the smelting of individual constituents and the formation of the final product. Here’s a step-by-step overview of how Hastelloy is industrially manufactured.

Step#1: Smelting

The first step in the manufacturing process of Hastelloy is the smelting of the numerous different metallic elements. 

Here, the prepared raw materials, having been specifically proportioned, are sent into the furnace where they are melted together at high temperatures (between 1600°C and 1800°C)

The common practice is to use an electric furnace or induction arc furnace depending on the target Hastelloy grade. 

Step#2: Casting

After melting, the next step is casting. This involves pouring the molten hastelloy into prefab billet or ingot molds to the cavity shapes. 

The molds are typically made of graphite or ceramic and are preheated to prevent the molten hastelloy from solidifying too quickly.

Step#3: Rolling

Here, the Hastelloy billets or ingots are again reheated to temperatures ranging from 1100°C to 1300°C and then rolled into flat sheets or bars. 

This process is known as hot rolling. The sheets or bars are then allowed to cool to room temperature.

Step#4: Forging

Forging Hastelloy involves reheating the rolled Hastelloy sheets or bars back to about 1300°C before shape-compressing them back into the desired final shape using forging presses or hammers. Forging further improves the strength and durability of the metal.

Step#5: Heat Treatment

Last but not least is the heat treatment. As the name suggests, the process involves heating the forged Hastelloy to temperatures ranging from 1050°C to 1150°C before controlled cooling. 

Heat treatment of the Hastelloy improves their mechanical properties, making them more resistant to oxidation and corrosion.

After the heat treatment process is completed, the Hastelloy parts are inspected for any defects, such as cracks or porosity. Any defective parts are rejected, and only the parts that meet the quality standards are used for further processing or applications.

Keep in mind that the 5-step process we described above is not a hard and fast rule. It’s more of a general guideline on how the process works. In reality, it can be more complex.

Different manufacturers will typically have their proprietary processes. But you’ll find they can all be broadly partitioned into those 5 steps.

Hastelloy vs Stainless Steel

Hastelloy and stainless steel are two excellent materials renowned for their anti-corrosion properties and high utility. Let’s take a quick close look at how these materials differ.

Hastelloy vs Inconel

Hastelloy and Inconel are superalloys formulated to overcome the limitations of naturally occurring materials. 

Both are excellent materials that are applicable across many industries and can even be substituted for one another depending on application parameters.

Applications of Hastelloy

The unique properties of Hastelloy alloys make them ideal for use in harsh environments where other materials might fail making them highly sought after across many industries.

Here are some of the most common applications of Hastelloy:

Chemical Processing

Chemical processes typically involve one or more highly reactive substances. On a larger industrial scale, this constraint places more strain on processing materials. Chemical processing companies have a high demand for stronger materials like Hastelloy for optimal production. 

The superalloys are in high use in this industry, where they provide excellent resistance to corrosion from the aggressive chemical environment resulting from production chemical reactions. 

They are commonly used in process equipment such as reactors, heat exchangers, distillation columns, and piping systems.

Aerospace

Hastelloys are one of the most powerful temperature-resistant materials on earth. 

They can maintain their full performance at super high-temperature levels without expanding significantly or creeping. This makes them highly suitable in aerospace and spacecraft where most products typically require materials with a high-temperature threshold.

Hasten alloys are commonly used to build jet engine components, rocket components, connectors, fasteners, and exhaust systems to mention but a few.

Oil and Gas

Oil and gas is another sector with high anti-corrosive threshold material requirements. You can use Hastelloy alloys in various fields. Some of which include upstream, midstream, and downstream applications. 

They are commonly used in downhole tools, production tubing, and other equipment that is exposed to corrosive environments.

Power Generation 

Power generation is synonymous with heat generation. Powerful power generation infrastructures can’t help but generate high levels of heat. It’s the physics of the process.

Hastelloys are used extensively in power generation applications to ensure the structural integrity of power generation infrastructures even at extreme temperature conditions. This includes fossil fuel power plants, nuclear plants, and renewable energy plants. 

Other hastelloy applications include;

• Pulp and paper 
• Mining
• Geothermal
• Pharmaceuticals and biotechnology

Conclusion

Hastelloy superalloys are an essential material used in a range of industries due to their exceptional resistance to corrosion, high-temperature strength, and excellent mechanical properties. 

With their unique properties, these alloys are a reliable and versatile solution for various applications. All things considered, it is safe to say that their significance will likely continue to grow as new applications are developed in response to changing technologies and industrial demands.