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High Alloy Stainless Steels

For many years, the 300 series stainless steels (SST) have been the workhorse alloys for corrosive applications. For severe applications, the nickel-base alloys were the next step up in corrosion resistance. The cost differential, however, was great (four to ten times, or more). In recent years, duplex and superaustenitic SSTs have started to fill this void as cost-effective alternatives.

High alloy SSTs are similar to the 300 series SSTs whereas they are iron base with significant additions of chromium, nickel, and molybdenum. To produce a duplex SST, the alloy chemistry is adjusted by increasing the chromium and molybdenum and reducing the amount of nickel, see the following figure. These changes result in both ferrite and austenite phases present in approximately equal amounts. By contrast, the 300 series SSTs are generally fully austenitic. Superaustenitic SST’s have the same structure as the common 300 series alloys, but have higher levels of elements such as chromium, nickel, molybdenum, copper and nitrogen.

High alloy SST’s are often used where chlorides or sour gas are encountered. Industries include pulp and paper, chemical, oil and gas, power, desalination, and marine.

Advantages of high alloy stainless steels are:

  • Superior stress corrosion cracking resistance and corrosion resistance in chloride environments.
  • Yield strengths significantly higher or even double that of annealed 300 series SST.
  • Duplex SST’s have inherently better resistance to stress corrosion cracking than 300 series single-phase alloys, because at least one of the phases is often resistant to cracking in a given environment.

Contact us for more information

If you are dealing with a corrosion problem in your valves and piping system, contact our inside sales team about a cost effective high alloy stainless steel solution.

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