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28 Chrome: Solid Solution Nickel Alloy

Common Names:

28CR, 2832, 928, Nic28, Sanicro 28, 1.4563, X1NiCrMo31-27-4, VM28, SAF 28, Alloy 28

Alloy Group

Solid Solution Nickel Alloy

Corrosion Resistance

High

Yield Strength

110

—

160

Wall Tolerance

0.875

Density

0.29

PREN

37.55

—

42.85

Additional Documentation

Alloy Details

28 Chrome (UNS N08028), also known as Alloy 28, is a cold-hardened nickel-based alloy designed for corrosion resistance in highly sour (H2S) environments with moderate chloride levels, providing high strength up to 350°F.

Compared to stainless steels, 28 Chrome offers superior resistance to the effects of H2S, making it suitable for use in downhole tubular components, packers, and other subsurface equipment in sour wells with high-pressure, high-temperature (HPHT) conditions, as well as in Acid Gas Injection (AGI) wells. It also exhibits exceptional resistance to pitting and crevice corrosion in environments with chlorides. However, it is crucial to assess all environmental factors, such as H2S, CO2, temperature, pH, and chloride concentrations, before selecting the appropriate material.

The alloy is classified as a type 4c alloy in MR0175/ISO15156, with no limitations for H2S partial pressure below 270°F and resistance to 200 psi H2S at 350°F.

Solid Solution Nickel Alloy

Nickel-base alloys are primarily employed in environments where the partial pressure of H2S exceeds 3 psi. These alloys are enhanced with increased levels of Nickel, Molybdenum, and other elements to extend their performance in harsh conditions involving high temperatures, H2S, and chlorides. Nickel alloys are approved for highly sour environments in accordance with NACE MR0175/ISO 15156. In the annealed condition yield strengths may range from 30 to 55 ksi. Pipe is typically supplied in the cold-hardened condition with yield strength between 110 and 160 ksi.

Chemical Composition

C
6
Carbon
0.03%
Si
14
Silicon
1%
P
15
Phosphorus
0.03%
S
16
Sulfur
0.03%
Cr
24
Chromium
26%‒28%
Mn
25
Manganese
2.5%
Fe
26
Iron
30.51%‒40.9%
Ni
28
Nickel
29.5%‒32.5%
Cu
29
Copper
0.6%‒1.4%
Mo
42
Molybdenum
3%‒4%

Specified Mechanical Properties

API 5CRA / ISO 13680 Group 3 Category 27-31-4
GradeYield
Strength
ksi		Tensile
Strength
ksi		Elongation
%		Hardness
HRC		NACE MR0175/ISO 15156
H2S Sour Service Limits
minmaxminminmax
1101101401151133Table A.14
Type 4c		No limit ≤ 270°F,
Refer to table for temperatures up to 450°F
1251251501301035
140140160145938140 Grade not recommended for sour service

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

Specified Mechanical Properties in Annealed Condition

Per ASTM B668
Tensile StrengthYield StrengthElongation
minimum, ksiminimum, ksiminimum, %
733140

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

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