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Understanding Heat-Resistant Superalloys

Understanding Heat-Resistant Superalloys

Although steel is the most widely used metal, there are hundreds of applications where the properties of steel and its alloys simply don’t provide the required strength and durability. Under certain conditions, steel is subject to hydrogen embrittlement and/or corrosion that can lead to material failure.

Hydrogen embrittlement is caused by carbon steel alloys absorbing hydrogen atoms or molecules during poorly executed manufacturing operations such as forming, coating, electroplating, welding, or cleaning processes. Hydrogen can also be introduced over time through environmental exposure to hydrocarbons, acids, and corrosive environments. Hydrogen embrittlement causes components to crack or fracture at stresses less than the metal’s yield strength. Surprisingly, high-strength steel alloys are the most vulnerable to hydrogen embrittlement.

Corrosion in steel alloys is caused by exposure to acids, moisture, and oxygen. This electrochemical reaction results from the tendency for metals to return to their natural state—iron in the case of steel. The corrosion rate is affected by ambient air temperature, humidity, and chemical fumes. Corrosion changes the surface microstructure of steel, making it brittle and flaky and causing it to lose mechanical strength.

Heat-Resistant Superalloys (HRSA) Meet The Requirements

Where steel alloys fall short in their ability to withstand certain extreme environments,  heat-resistant superalloys meet the requirements. These alloys excel in their ability to withstand high temperatures and corrosive environments.

Two heat-resistant superalloys used frequently by San Francisco manufacturers, machine shops, and fabricators are Hastelloy and Inconel. These heat-resistant superalloys have similar properties, with relatively equal proportions of nickel and chromium in each alloy. Hastelloy and Inconel are available in a range of alloys, each with varying chemical compositions. The table below shows the variations (given in percentages) in the chemical composition of two heat-resistant alloys.

Hastelloy X


Inconel 625


Inconel 718


Nickel 47-51 58-71 50-55
Molybdenum 8-10 8-10 2.8-3.3
Chromium 20.5-23 20-23 17-21
Iron 17-20 5 Balance
Cobalt 0.5-2.5 1 <1
Silicon 1 <1 <0.35
Manganese 1 <1 <0.35
Tungsten 0.2-1
Nobium + Tantalum 3.15-4.15 4.75-5.5
Other elements each <1 each <1 each <1

Hastelloy Nickel-Chromium-Iron-Molybdenum Superalloy

Hastelloy is a registered trademark of Haynes International that applies to more than 20 different nickel-based superalloys offering exceptional resistance to corrosion, oxidation, and reducing agents at high temperatures. The addition of molybdenum improves performance at high temperatures and makes Haselloy suitable for welding applications. Some Hastelloy alloys can be used for components that are subjected to temperatures as great as 2,200°F.

The high molybdenum content also contributes to crevice corrosion and pitting resistance. Hastelloy offers good resistance to chromic, sulfuric, hydrochloric, hydrofluoric, and nitric acids. Its properties make it applicable for components and assemblies used in chemical processing, gas turbines, oil and gas production, pharmaceutical manufacturing, and components subject to high mechanical stress in saltwater environments.


InconelInconel is a registered trademark of Special Metals Corporation for a series of nickel-based, corrosion-resistant, high-temperature superalloys. When heated, Inconel forms a thick, stable, passivating oxide layer which protects the surface from future attack. The alloy maintains strength over a wide temperature range, with some Inconel alloys maintaining their strength over a range of cryogenic temperatures to 1,800°F.

Inconel offers superior resistance to severely corrosive environments as well as high oxidation resistance at high temperatures, tensile strength, and consistent mechanical properties across extremely low and high temperatures. These properties make Inconel suitable for the manufacture of components used in chemical and petrochemical processing, gas turbines, nuclear reactors, sour gas pipelines, waste treatment plants, and components subject to high mechanical stress in marine environments.

Purchase Heat-Resistant Superalloys at Discount

The cost of heat-resistant superalloys can be significantly higher than carbon and stainless steel alloys that don’t perform as well in corrosive, high-temperature environments. Machine shops, fabricators, and welders in the San Francisco Bay area can take advantage of local metal suppliers like Industrial Metal Service who offer heat-resistant alloys at discounted prices. They are able to do this by buying usable Hastelloy and Inconel scraps—remnants with dimensions too small for further use by manufacturers, but more than suitable for dozens of other machining or welding applications—and selling them at discount prices.


The chemical content of the heat-resistant superalloys is verified using X-ray fluorescence technology to ensure you’re receiving high-quality materials. Industrial Metal Service can cut Hastelloy and Inconel remnants to size, making it easier for shops that don’t have industrial-level sawing resources to immediately begin machining the custom-cut remnants.

Bay Area Delivery or Nationwide Shipping

Whether you need an ongoing supply of heat-resistant superalloys, a one-time order for a special project, or a last-minute order of Inconel to machine a prototype component, Industrial Metal Service provides regular delivery within the San Francisco Bay Area. You’re also welcome to stop by our warehouse in San Jose and browse our extensive inventory of heat-resistant alloys, aluminum, angle iron, titanium, and copper. If you’re located in an area without a convenient, local metal supplier, we ship metals nationwide, with no minimum order quantity required.

Call us today to discuss your metal supply requirements. We look forward to working with you.

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Published by IMS Team

Industrial Metal Service has decades of experience and over 1.1 billion pounds of metal sold and recycled. Our founder, Jeff, has spent his life in the industry and prides himself on offering fair, efficient, trustworthy, knowledgeable, outstanding customer service. We offer metal salesmetal recycling pickup service, and other associated services, such as precise metal sawing, machinery teardown, and warehouse cleanupGive us a call and we’ll get it done.