C22

The composition of the weld deposit, Ni-22Cr-13.5Mo-3W, has been developed to be compatible with the nickel-based alloy more commonly known as alloy C22. The high molybdenum content is comparable to that of alloys C276 and C4; however, performance in a wide range of more oxidizing environments is significantly improved by increasing chromium to 22% in alloy C22. Alloy C22 also offers a robust, niobium-free (Nb) metal deposit for dissimilar welds between superaustenitic and superduplex stainless steels or between these and nickel-based alloys. Some regulations have prohibited or limited the use of alloy 625 consumables for such applications, as harmful Nb-rich precipitates can form in the diluted or partially mixed regions near the edges of the fusion zone. Applications of alloy C22 in highly corrosive environments include scrubbers for flue gas desulfurization (FGD), digesters and equipment for paper production, chemical process plants, corrosion-resistant overlays, as well as offshore environments and the petrochemical sectors. Typically, preheating is not required; it is preferable to maintain an interpass temperature below 100 °C and heat inputs below 1 kJ/mm.

Nickel base 22%Cr-13.5%Mo-3%W, alloy C22.

Solid solution strengthened high nickel austenite, with some microsegregation typical of as deposited weld metal.

• EN W.Nr.: 2.4602 (NiCr21Mo14W), 2.4811, 2.4836 (NiCr20Mo15), 2.4697 (G-NiCr20Mo15), 2.4610 (NiMo16Cr16Ti), 1.4529, 1.4565, 1.4575, 1.4652
• ASTM: A494 CX2MW (cast)
• UNS: N06022, N06455, S31254, S31266, S32654, S34565, N08367, N08925, N08926
• PROPRIETARY: Hastelloy® Alloy C-22, C-4 (Haynes International Inc), Nicrofer 5621hMoW (VDM), Inconel® 622 (Special Metals), 254SMO, 654SMO (Outokumpu), Uranus B66 (Usinor Industeel)

The welding process for this subfamily involves techniques that ensure high corrosion resistance and reliability in demanding environments. The low heat input method is crucial to avoiding material degradation and maintaining the integrity of the welds, especially in applications involving dissimilar materials.