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Super Duplex 25 Chrome: Duplex Stainless Steel

Common Names:

25CRS, F61, Ferralium 255, F53, F55, S32760, S32750, SAF 2507, 1.4501, 1.441, 1.4507, S39277, AF 918, VM25S, Z100, 918, Super 25 Chrome

Alloy Group

Duplex Stainless Steel

Corrosion Resistance

Moderate

Yield Strength

80

—

160

Wall Tolerance

0.875

Density

0.28

PREN

40.4

—

48.95

Additional Documentation

Alloy Details

Super Duplex 25 Chrome alloys, including 25CRW and 25CRS, are cold-hardened duplex stainless steels designed for corrosion resistance in sweet (CO2) and moderately sour (H2S) environments with high chloride concentrations, providing high strength up to 450°F.

The “Super” designation signifies a Pitting Resistance Equivalent Number (PREN) of ≥40, offering enhanced protection against H2S and localized corrosion from high chloride levels and/or oxygen, compared to standard 25 Chrome. As a result, these alloys are commonly used in tubing and liners for seawater and water injection wells. However, it is important to evaluate all relevant environmental factors, including H2S, CO2, temperature, pH, and chloride concentration, before finalizing material selection.

These alloys are classified under MR0175/ISO15156 as duplex stainless steels with a Pitting Resistance Equivalent Number (PREN) ≥40, suitable for environments with H2S partial pressures up to 3.0 psi.

Duplex Stainless Steel

Duplex Stainless Steels are two-phase alloys, combining roughly equal amounts of austenite and ferrite. These steels typically contain 20% to 30% chromium, along with molybdenum, nitrogen, and other elements that enhance resistance to pitting and crevice corrosion. As a result, they are ideal for applications in environments with high chloride content. In their annealed state, duplex steels offer yield strengths ranging from 65 to 100 KSI, while cold working can boost the yield strength up to 160 ksi.

Super Duplex Stainless Steels offer improved resistance to elevated temperatures and chloride levels, making them well-suited for demanding conditions such as seawater or water injection wells. Defined by a Pitting Resistance Equivalent Number (PREN) greater than 40, these alloys provide exceptional protection against high chlorides and dissolved oxygen.

Chemical Composition

C
6
Carbon
0.03%
N
7
Nitrogen
0.2%‒0.3%
Si
14
Silicon
1%
P
15
Phosphorus
0.03%
S
16
Sulfur
0.01%
Cr
24
Chromium
24%‒26%
Mn
25
Manganese
1%
Fe
26
Iron
57.63%‒65.8%
Ni
28
Nickel
6%‒8%
Cu
29
Copper
0.5%‒1%
Mo
42
Molybdenum
3%‒4%
W
74
Tungsten
0.5%‒1%

Specified Mechanical Properties

API 5CRA / ISO 13680 Group 2 Category 25-7-4
GradeYield
Strength
ksi		Tensile
Strength
ksi		Elongation
%		Hardness
HRC		NACE MR0175/ISO 15156
H2S Sour Service Limits
minmaxminminmax
80801051102028Table A.24
(annealed)		H2S ≤ 3.0 psi,
Temp ≤ 450°F
90901051152030
1101101401251236Table A.25
(cold-worked)		H2S ≤ 3.0 psi,
Cl ≤ 120g/l
1251251451301036
140140160145938140 Grade not recommended for sour service

* Non-standard mechanical properties and grades are made available upon agreement.

Per ASTM A789 / A790
Tensile StrengthYield StrengthElongationHardness
minimum, ksiminimum, ksiminimum, %HRC
116801532

* Higher strength properties can be provided in the cold hardened condition.

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