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Alloys 945 & 945X an ultimate corrosion defence


Incoloy Alloy 925 and 945X are exceedingly strong, age-hardenable nickel-iron-chromium alloys designed for use in oil & gas applications, particularly downhole oil well hardware where these requirements of service are extremely high and becoming ever more demanding. A downhole hanger must support the weight of the entire oil well casing and must have strength and resistance to general and localized corrosion under sour well conditions. Traditionally Alloys 725, 718 and 925 have met these demanding requirements for tubing hangers, liner hangers and polished bore receptacles.
In an article to be published in the July edition of Stainless Steel World magazine, Jan Ward of Corrotherm International Ltd. tell us that the development of 945 and 945X has been driven by the need from modern operators for a new material that was equal to 718 and 925 but that could withstand the higher requirements of deeper drilling. The design criteria for 945 were built around the need for corrosion resistance at least as good as 925 or 718. In addition the material must not have a tendency to form inter-granular second phase as it degrades aqueous corrosion resistance. Crucially any replacement must have a minimum 130 ksi yield. In addition to this, as always, operators were also looking for lower costs.
Alloy 925 has a 110 ksi min yield and Alloy 718 has a 125 ksi min yield. Whereas Alloy 945 has a 130 ksi min yield and 945X has a min yield of 140ksi with an excellent combination of ductility and impact strength in the solution treated and aged condition. The alloy was tested under various NACE environments and based on this set of testing the alloy was incorporated into NACE MR0175/ISO-15156 to level IV. Following more recent tests the alloy has also passed NACE level VII and level VI at 450F. Alloy 945 and 945X is vacuum induction melted and VAR re-melted, then subject to a two-step age hardening process. The chemical compositions of Alloys 945 and 945X are given below along with comparisons with other nickel alloys with a 40%+ nickel content.