When you need fastener that can stand up to the harshest conditions possible, a tried and true material is the safest way to go. That’s where superalloys like Hastelloy® come in.
Hastelloy® is a nickel-based superalloy created by Cabot Corporation for use in extreme conditions.
Superalloy is a term used for many nickel-based alloys used for intense conditions not suitable for more common metals. The term originated from the materials in military plane superturbochargers in WWII produced by General Electric. These materials needed to endure high temperatures and perform flawlessly to ensure the planes stayed in the air.
Today, this term is used for alloys that can operate closer to their melting point than common materials (Up to 90%). An issue with common alloys is that the misalignment of crystal boundaries within the metal cause a grain structure to form. This grain structure leads to poor creep resistance and greatly limited the capability of the material. Modern superalloys are cast as a single-crystal to eliminate this problem.
What is Hastelloy
Hastelloy is a brand name used to refer to a corrosion-resistant line of nickel-based alloys including C-276, C-22, and alloy X. Each variation is formulated for specific properties needed to perform under extremely harsh conditions. The basis for the alloy is a mixture of nickel, molybdenum, and tungsten.
One major advantage of Hastelloy’s formulation is the material’s ability to resist chloride stress corrosion cracking (CLSCC). CLSCC can cause many austenitic stainless steels to crack when used during chemical or petrochemical processing. The nickel-base minimizes this effect and with modern alloys like C-276, allows the material to be welded without compromising composition.
Another advantage of the Hastelloy formulation is the material’s excellent overall chemical resistance. The high amounts of chromium and molybdenum cause the material to be unaffected by almost all chemicals including oxidizing and non-oxidizing acids, chlorides, halides, and sulfides. This makes the material an outstanding choice for use in oil and gas extraction and processing applications.
Military jet engine combustion chambers can reach operating temperatures of up to 2,000 °C, or 3,632 °F. The gas running over the turbines can reach temperatures of 1,700 °C or 3,100 °F. While the melting point of Hastelloy is only about 1,350 °C, it retains its mechanical properties until it reaches 90% of that melting point. This means the parts only need cooled to around 1,200 °C instead of 900 °C for stainless steel to be used or below 600 °C for titanium to be used.
For space applications, the temperature range is even greater. Haynes International claims that during the space shuttle program that launched the Hubble Telescope and participated in constructing the International Space Station, 7 parts in the engine were made from Hastelloy B, and Hastelloy C-22 was used to create the bellows for the fuel lines used during takeoff.
Hastelloy was also used to create the engine valves in Charles Lindberg’s Spirit of St. Louis.
Hastelloy is commonly used in chemical processing facilities across the planet due to the material’s high corrosion resistance. In the 1980s and 1990s, several alloys were created specifically for use in this industry.
C-4 was created during this time and is the most microstructurally stable nickel-based alloy available. This means that it can be welded without any adverse effects on the chemical resistance of the part. C-22 is also used due to the alloy’s high chromium content. This creates a high resistance to chloride-induced pitting that eliminates stainless steels from being used.
C-2000 has copper deliberately added to the structure to increase resistance to sulfuric acid and a high chromium content to increase the resistance to oxidizing chemicals as well as dissolved oxygen.
G-35 was created specifically for use in fertilizer production and offers superior phosphoric acid resistance compared to any other material on the market. After testing in real-world solutions, this has become the standard for the industry.
Oil and Gas applications
C-22HS is used for high pressure, high-temperature oil and gas wells such as offshore drilling operations. This alloy performs at the maximum chemical resistance, hardness, and yield strength specifications currently used in the industry.
One of the main uses for Hastelloy alloys worldwide is industrial gas turbines. It can be used in almost all parts of a gas turbine including seals, rings and shrouds for the hot section, combustors, and exhausts.
Hastelloy can also be used to reduce emissions and improve the efficiency of coal-powered plants by using Advanced Ultra supercritical systems. While the technology is still being developed and materials are still being chosen nickel-based superalloys such as Hastelloy are being considered.
Hastelloy is currently used in specific, critical components in other industries. These uses include industrial heating, naval nuclear submarines, waste treatment, mining and mineral processing, and glass processing. Hastelloy is chosen for these industries because of the extreme conditions experienced by these parts including aggressive chemical attacks and high temperatures.
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