Superalloys and Where and Why Are They Commonly Used

Superalloys are known for their ability to tolerate high-temperature environments such as jet and rocket engines. They are made primarily of nickel with the addition of alloying elements such as molybdenum, chromium, and iron to provide strength and durability at high temperatures. Four of the superalloys used most frequently by manufacturers and machine shops in the San Francisco Bay area are Hastelloy, Inconel, Invar, and Monel.

While all of these superalloys hold up well in high temperatures, differences in their metallurgy make each suitable for specific applications. The characteristics and uses of Hastelloy, Inconel, Invar, and Monel are summarized below to provide a better understanding of superalloys and where and why they are commonly used.

Hastelloy Nickel-Molybdenum Alloy

Chemical composition: 57% nickel, 15-17% molybdenum, 14.5-16.5% chromium, 4-7% iron, 3-4.5% tungsten, 2.5% cobalt, and 1% manganese, with other alloying elements, each less than 1%

Characteristics

• Oxidation resistance up to 2,200°F
• Chloride stress-corrosion cracking resistance
• Resistance to reducing or carburizing atmospheres

Machinability

• Work hardens rapidly as a result of generating high heat during cutting
• Workpiece and tool should be held rigid
• The machine should be overpowered as much as possible
• Use high-pressure coolant and through-the-tool coolant systems

Applications

• Widely used for components in the combustion zone of gas turbine engines—combustor cans, spray bars, nozzle vanes, turbine blades, and afterburners
• Chemical processing equipment

Inconel Nickel-Chromium Alloy

Chemical composition: 50-55% nickel, 17-21% chromium, 4.75-5.5% niobium, 2.8-3.3% molybdenum, and 1% cobalt, with other alloying elements each less than 1%

Characteristics

• Excellent corrosion resistance, particularly in saltwater environments
• Forms a thick, stable, passivating oxide layer when heated, protecting the surface from further attack
• Retains strength over a wide range of high temperatures where steel or aluminum are likely to succumb to creep
• Superior to steel in maintaining tensile strength up to 2,000°F

Machinability

• Use aggressive but slow cuts with a hard tool to minimize the number of passes required
• Water-jet or laser grinding are the preferred options for forming components to their final shape and finish

Applications

• Parts and components subjected to high temperature and high mechanical loads
• Gas turbine blades, seals, and combustors
• Turbocharger rotors and seals
• Components used in saltwater environments or maritime locations
• Electric submersible well pump motor shafts
• Chemical processing and pressure vessels
• Heat exchanger tubing, steam generators, and components in nuclear-pressurized water reactors

Invar Iron-Nickel Alloy

Chemical composition: 62% iron, 32% nickel, and 5.5% cobalt, with other alloying elements each less than 1%

Characteristics

• Very low coefficient of thermal expansion, similar to glass and ceramics

Machinability

• Machine at slower speeds using sharp and rigidly supported tooling

Applications

• Parts and components requiring high dimensional stability such as engine valves, seismic creep gauges, precision instruments, and aerostructure molds
• Bimetals for thermostats, circuit breakers, motor controls, temperature compensating springs, and aerospace and automotive controls
• Sealing (pin feedthroughs, packaging, and lids) for semiconductors and microprocessors
• Containers that resist cryogenic shrinkage when transporting liquified natural gas

Monel Nickel-Copper Alloy

Chemical composition: 52-67% nickel, 28-34% copper, 2.5% iron, and 1% manganese, with other alloying elements each less than 1%

Characteristics

• Stronger than pure nickel
• Resistant to corrosion by seawater and acids
• Excellent mechanical properties at subzero temperatures
• Expensive and used for applications where lower-cost materials are unsuitable

Machinability

• It’s recommended to work at slow speeds and feed rates

Applications

• Piping systems, pump shafts, valves, bolts, and strainer baskets in saltwater and acidic environments
• Used where strength is required but stainless steel cannot be used because of corrosion resulting from stainless contact with the aluminum in saltwater environments
• Screw-machine products, fasteners, and oil well tools

A Local, Reliable Source for Superalloys at Discount Prices

With most of these superalloys trademarked and produced by a single manufacturer, you’ll pay a premium when you source the materials directly from the mill. Machine shops and fabricators that don’t require high volumes of superalloys for their production schedules can benefit by purchasing verified superalloys at discounted prices from a local metal supplier.

Industrial Metal Service is a long-established supplier of high-quality metals for San Francisco Bay Area manufacturers, machine shops, fabricators, and welders. We’re unique because the recycling arm of our business allows us to acquire superalloy remnants remaining from major manufacturing processes, trim them to usable dimensions, and sell them at discounted prices.

Verified Superalloy Composition and Quality

We use x-ray fluorescence to verify the composition of these metals, so you’re assured of high-quality materials when you source from us. We also offer precision sawing services for shops that don’t have industrial quality sawing resources in-house and simply want to outsource sawing to shorten their production process.

Whether you need a single piece of Monel to machine a custom driveshaft, Inconel round bar to meet a special production contract, or a regular supply of Invar for long-term production schedules, Industrial Metal Service is conveniently located in San Jose. We provide delivery within the Bay Area and have often “saved the day” for shops in need of last-minute metal supplies to finish a project.

Industrial Metal Service is open Monday through Friday from 7 AM to 4 PM and Saturday from 8 AM to 12 PM. You’re welcome to stop by our warehouse and take a look at our inventory of superalloys as well as aluminum, steel, copper, brass, and titanium available at discount prices.Give us a call at 408-294-2334 to discuss your specific metal supply requirements.

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