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Today there are roughly 200 different grades of stainless steel, all of which fall within one of the five families of stainless steel: Austenitic, Ferritic, Martensitic, Duplex, or Precipitation Hardening.
Previously, we explored austenitic, martensitic, and ferritic stainless steels, detailing where to use some common grades and why. Here, the focus is on, precipitation hardening and duplex stainless steel, rounding out the five families of stainless steel.
All stainless steels are iron-based alloys containing at least 10.5% chromium. The rest of the makeup is defined by various alloying elements, which control the microstructure of the alloy. For precipitation hardening and duplex stainless steels, that make up includes chromium, nickel, copper, and more.
Characteristics: Precipitation hardening is a heat treatment technique used to increase the yield strength of malleable materials, so it is extremely strong and resistant to corrosion. Duplex stainless steel is extremely corrosion resistant and work hardenable alloys.
Now let’s take a closer look at four grades to see which are best suited for what applications – and why.
Alloying elements: Chromium, nickel, copper, niobium
Commonly used grades: 2205 for duplex and 17-4 for precipitation hardening.
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Precipitation Hardening:
17-4/Type 630
Where to use it: Helicopter deck platforms, the paper industry, turbine blades, and nuclear waste casks.
Why: A grade that is precipitation hardening, this combines high strength and hardness with corrosion resistance. Low-temperature heat treatment eliminates scaling and prevents excessive warpage.
17-4 Double Aged H1150
Where to use it: Air spray guns, golf club heads, propeller shafts, suppressors, and silencers.
Why: High strength and excellent corrosion resistance makes this alloy extremely versatile.
15-5
Where to use it: Gears, turbine blades, valves, and other engine components, and nuclear waste casks.
Why: This grade has high strength and hardness as well as excellent corrosion resistance and excellent transverse toughness.
Duplex:
2205
Where to use it: Power generation, oil and gas, chemical processing and desalination.
Why: A nitrogen enhanced alloy, this grade has excellent resistance to general corrosion and chloride stress corrosion cracking.
