COMMON TRADE NAMES: Alloy 28, 28Cr, Sanicro 28™, SAF 28®, VM® 28, Nic28, NiCro 31/27
28 Chrome (UNS N08028), or Alloy 28, is a cold hardened nickel-based alloy intended for corrosion resistance in highly sour (H2S) environments with moderate chloride content, requiring high strength up to 350°F.
28 Chrome offers increased resistance to the effects of H2S relative to stainless steels allowing its use as downhole tubular components, packers, and other subsurface equipment in sour wells with high-pressure and high-temperature (HPHT) conditions and Acid Gas Injection (AGI) wells. In addition, it has a high resistance to pitting and crevice corrosion in the presence of chlorides. However, all environmental factors, including H2S, CO2 , temperature, pH, and chloride concentration, should be considered before final material selection.
The alloy is classified in MR0175/ISO15156 as a type 4c alloy, with no restrictions to a partial pressure of H2S below 270°F and resistant to 200 psi H2S at 350°F.
|≤ 0.03||26 - 28||29.5 - 32.5||BAL||≤ 2.5||≤ 1||3 - 4||0.6 - 1.4||≤ 0.03||≤ 0.03|
|Steel Making||Made by electric furnace process or blast furnace followed by Vacuum Oxygen Decarburization (VOD) process or Argon Oxygen Decarburization (AOD) Process|
|Pipe Making||Manufactured by traditional tube manufacturing processes, High strength tubulars should be furnished in cold worked condition|
|Heat Treatment||Solution Annealing Process before final cold drawing|
API 5CRA / ISO 13680 Group 3 Category 27-31-4
|NACE MR0175/ISO 15156
H2S Sour Service Limits
|No limit ≤ 270°F,
Refer to table for temperatures up to 450°F
|140||140||160||145||9||38||140 Grade not recommended for sour service|
|Elastic Modulus||psi x 106||28.3||27.6||26.3|
|Thermal Conductivity||Btu/ft h °F||5.5||7||8.5|
|Specific Heat||Btu/lb °F||0.11||0.12||0.12|