When can Hastelloy not be used?
What are Hastelloy Metals and Alloys?
A metal, such as silver or copper, is a pure element, while an alloy is a man-made mixture of two or more elements. While stainless steel and Hastelloy can be used for similar applications, there are some key differences between these materials.
Differences Between Stainless Steel and Hastelloy
Nickel and molybdenum are the main components of any Hastelloy alloy. Nickel is a naturally occurring silvery metal with a melting point of 2,651ºF. It is highly resistant to corrosion.
Similarly, molybdenum is a shiny, silvery metal with an extremely high melting point of 4,752ºF. It is used to enhance the strength, electrical conductivity, and hardness of certain alloys.
On the other hand, stainless steel is strengthened with nickel and chromium. Chromium acts as a rust inhibitor. However, the higher nickel and molybdenum content makes Hastelloy metals and alloys more corrosion resistant than stainless steel, especially at high temperatures.
Hastelloy Optimization
While all grades of Hastelloy are corrosion resistant, some grades have been optimized for specific purposes. The mechanical properties of different grades of alloys determine how they will perform in deep drawing, stamping, and welding processes.
Hastelloy Alloy Grades
In addition to containing nickel and molybdenum, different grades of Hastelloy may contain certain percentages of iron, aluminum, tungsten, carbon, titanium, chromium, and other elements. The most widely used and versatile Hastelloy alloy is the C-type.
Hastelloy X alloy was formulated in 1952 and is a newer high-temperature alloy grade compared to the other alloys. It contains a higher percentage of iron to improve oxidation resistance, formability, and high-temperature strength. It can also be cold rolled to meet the required tempering properties; however, it cannot be hardened by heat treatment.
B-Type Alloys
B-Type alloys are known for their high percentages of nickel and molybdenum. Like nickel, molybdenum has high corrosion resistance. It is known for its ductility and has one of the highest melting points of all naturally occurring elements. These alloys are formulated to withstand extreme reducing conditions, such as hydrochloric, hydrobromic, and sulfuric acid environments.
B-2 Alloy
This grade of alloy typically contains 65% nickel, 30% molybdenum, and small amounts of iron, carbon, cobalt, chromium, manganese, silicon, phosphorus, and sulfur. It has excellent resistance to hydrochloric acid corrosion at any concentration or temperature. However, it is not resistant to oxidants.
B-3 Alloy
The average composition of B-3 alloy is 65% nickel, 30% molybdenum, and trace amounts of manganese, cobalt, and chromium. It has excellent resistance to pitting and corrosion compared to B-2 alloy, as well as excellent thermal stability. Like B-2 alloy, it is likely to deteriorate prematurely if exposed to oxidants.
C-Type Alloys
Alloys belonging to the C series have high percentages of nickel, molybdenum, and chromium. The addition of chromium improves the formability of these types of alloys, allowing them to withstand high temperatures and reducing atmospheres. Most C-type alloys can be formed using different cold and hot working methods, such as deep drawing, press forming, and stamping.
C-4 Alloy
C-4 alloy consists of about 60% nickel, 18% chromium, 16% molybdenum, 3% iron, and 2% cobalt. The remaining ingredients include silicon, sulfur, carbon, titanium, and other elements. In addition to corrosion resistance, it has high ductility, making it suitable for deep drawing.
C-22 Alloy
C-22 alloy is one of the most commonly used alloys in flue gas desulfurization systems and pharmaceutical reaction vessels. Typically, it contains about 58% nickel, 20% chromium, 13% molybdenum, 3.5% iron, 3% tungsten, and 2.5% cobalt, as well as other trace elements. It is widely used for its weldability; however, it should not be used in environments above 1,250ºF.
C-276 Alloy
This alloy is the standard for petrochemical processing applications. The majority of its composition is nickel. However, it contains an average of 16% molybdenum, 15% chromium, 5.5% iron, 4% tungsten, and trace percentages of other elements. It has excellent resistance to pitting, intergranular corrosion, and oxidants. However, it does not perform well in hot concentrated nitric acid environments.
Advantages of Hastelloy
Manufacturers in multiple industries benefit from using Hastelloy metals and alloys due to their durability, excellent corrosion resistance, and high temperature resistance. While other materials can also do the job, these superalloys are easy to source and can be used in a variety of manufacturing processes.
Applications of Hastelloy
Hastelloy metals and alloys are widely used in multiple industries due to their enhanced mechanical properties. Due to their ability to withstand moderate to severe corrosion, Hastelloy alloys are used in many welding, aerospace engineering, and chemical processing applications.
Aerospace
Many Hastelloy alloys are ideal for aerospace applications due to their creep resistance and low expansion at high temperatures. Common applications of Hastelloy alloys in the aerospace industry include structural honeycombs, fasteners, connectors, engine components, and more.
Chemical Processing
Chemical processing is one of the largest manufacturing industries in the United States. It produces a wide variety of common products, from prescription drugs to cosmetics. In 2019, the chemical processing industry spent $10.1 billion on research and development. As technology and products evolve, the demand for better and stronger materials grows.
Hastelloy alloys can be used to make equipment parts in reactors such as towers, piping systems, pressure vessels, heat exchangers, and more. Due to their excellent corrosion resistance, they can withstand many of the daily chemical reactions that occur in these facilities.
Gnee Steel is a trusted leader in steel, offering a wide selection of nickel-based alloys. They provide customers with the support of metallurgists, as well as an extensive database of alloys and materials.
